Examining the role of MEDLINE as a patient care information resource: an analysis of data from the Value of Libraries study.

OBJECTIVE: This study analyzed data from a study on the value of libraries to understand the specific role that the MEDLINE database plays in relation to other information resources that are available to health care providers and its role in positively impacting patient care. METHODS: A previous study on the use of health information resources for patient care obtained 16,122 responses from health care providers in 56 hospitals about how providers make decisions affecting patient care and the role of information resources in that process. Respondents indicated resources used in answering a specific clinical question from a list of 19 possible resources, including MEDLINE. Study data were examined using descriptive statistics and regression analysis to determine the number of information resources used and how they were used in combination with one another. RESULTS: Health care professionals used 3.5 resources, on average, to aid in patient care. The 2 most frequently used resources were journals (print and online) and the MEDLINE database. Using a higher number of information resources was significantly associated with a higher probability of making changes to patient care and avoiding adverse events. MEDLINE was the most likely to be among consulted resources compared to any other information resource other than journals. CONCLUSIONS: MEDLINE is a critical clinical care tool that health care professionals use to avoid adverse events, make changes to patient care, and answer clinical questions.

Library and information services: impact on patient care quality.

PURPOSE: The purpose of this paper is to explore library and information service impact on patient care quality. DESIGN/METHODOLOGY/APPROACH: A large-scale critical incident survey of physicians and residents at 56 library sites serving 118 hospitals in the USA and Canada. Respondents were asked to base their answers on a recent incident in which they had used library resources to search for information related to a specific clinical case. FINDINGS: Of 4,520 respondents, 75 percent said that they definitely or probably handled patient care differently using information obtained through the library. In a multivariate analysis, three summary clinical outcome measures were used as value and impact indicators: first, time saved; second, patient care changes; and third, adverse events avoided. The outcomes were examined in relation to four information access methods: first, asking librarian for assistance; second, performing search in a physical library; third, searching library's web site; or fourth, searching library resources on an institutional intranet. All library access methods had consistently positive relationships with the clinical outcomes, providing evidence that library services have a positive impact on patient care quality. ORIGINALITY/VALUE: Electronic collections and services provided by the library and the librarian contribute to patient care quality.

ß-Actin mRNA compartmentalization enhances focal adhesion stability and directs cell migration.

Directed cell motility is at the basis of biological phenomena such as development, wound healing, and metastasis. It has been shown that substrate attachments mediate motility by coupling the cell's cytoskeleton with force generation. However, it has been unclear how the persistence of cell directionality is facilitated. We show that mRNA localization plays an important role in this process, but the mechanism of action is still unknown. In this study, we show that the zipcode-binding protein 1 transports ß-actin mRNA to the focal adhesion compartment, where it dwells for minutes, suggesting a means for associating its localization with motility through the formation of stable connections between adhesions and newly synthesized actin filaments. In order to demonstrate this, we developed an approach for assessing the functional consequences of ß-actin mRNA and protein localization by tethering the mRNA to a specific location-in this case, the focal adhesion complex. This approach will have a significant impact on cell biology because it is now possible to forcibly direct any mRNA and its cognate protein to specific locations in the cell. This will reveal the importance of localized protein translation on various cellular processes.

An unbiased analysis method to quantify mRNA localization reveals its correlation with cell motility.

Localization of mRNA is a critical mechanism used by a large fraction of transcripts to restrict its translation to specific cellular regions. Although current high-resolution imaging techniques provide ample information, the analysis methods for localization have either been qualitative or employed quantification in nonrandomly selected regions of interest. Here, we describe an analytical method for objective quantification of mRNA localization using a combination of two characteristics of its molecular distribution, polarization and dispersion. The validity of the method is demonstrated using single-molecule FISH images of budding yeast and fibroblasts. Live-cell analysis of endogenous ß-actin mRNA in mouse fibroblasts reveals that mRNA polarization has a half-life of ~16 min and is cross-correlated with directed cell migration. This novel approach provides insights into the dynamic regulation of mRNA localization and its physiological roles.

Regulation of local expression of cell adhesion and motility-related mRNAs in breast cancer cells by IMP1/ZBP1.

Metastasis involves tumor cell detachment from the primary tumor, and acquisition of migratory and invasive capabilities. These capabilities are mediated by multiple events, including loss of cell-cell contact, an increase in focal adhesion turnover and failure to maintain a normal cell polarity. We have previously reported that silencing of the expression of the zipcode-binding protein IMP1/ZBP1 in breast tumor patients is associated with metastasis. IMP1/ZBP1 selectively binds to a group of mRNAs that encode important mediators for cell adhesion and motility. Here, we show that in both T47D and MDA231 human breast carcinoma cells IMP1/ZBP1 functions to suppress cell invasion. Binding of ZBP1 to the mRNAs encoding E-cadherin, ß-actin, α-actinin and the Arp2/3 complex facilitates localization of the mRNAs, which stabilizes cell-cell connections and focal adhesions. Our studies suggest a novel mechanism through which IMP1/ZBP1 simultaneously regulates the local expression of many cell-motility-related mRNAs to maintain cell adherence and polarity, decrease focal adhesion turnover and maintain a persistent and directional motility.

A transgenic mouse for in vivo detection of endogenous labeled mRNA.

Live-cell single mRNA imaging is a powerful tool but has been restricted in higher eukaryotes to artificial cell lines and reporter genes. We describe an approach that enables live-cell imaging of single endogenous labeled mRNA molecules transcribed in primary mammalian cells and tissue. We generated a knock-in mouse line with an MS2 binding site (MBS) cassette targeted to the 3' untranslated region of the essential ß-actin gene. As ß-actin-MBS was ubiquitously expressed, we could uniquely address endogenous mRNA regulation in any tissue or cell type. We simultaneously followed transcription from the ß-actin alleles in real time and observed transcriptional bursting in response to serum stimulation with precise temporal resolution. We tracked single endogenous labeled mRNA particles being transported in primary hippocampal neurons. The MBS cassette also enabled high-sensitivity fluorescence in situ hybridization (FISH), allowing detection and localization of single ß-actin mRNA molecules in various mouse tissues.

Feedback regulation between zipcode binding protein 1 and beta-catenin mRNAs in breast cancer cells.

ZBP1 (zipcode binding protein 1) is an RNA-binding protein involved in many posttranscriptional processes, such as RNA localization, RNA stability, and translational control. ZBP1 is abundantly expressed in embryonic development, but its expression is silenced in most adult tissues. Reactivation of the ZBP1 gene has been reported in various human tumors. In this study, we identified a detailed molecular mechanism of ZBP1 transactivation in breast cancer cells. We show that beta-catenin, a protein that functions in both cell adhesion and transcription, specifically binds to the ZBP1 promoter via a conserved beta-catenin/TCF4 response element and activates its gene expression. ZBP1 activation is also closely correlated with nuclear translocation of beta-catenin in human breast tumors. We further demonstrate feedback regulation by finding that ZBP1 physically associates with beta-catenin mRNA in vivo and increases its stability. These experiments suggest that in breast cancer cells, the expression of ZBP1 and the expression of beta-catenin are coordinately regulated. beta-Catenin mediates the transcription of the ZBP1 gene, while ZBP1 promotes the stability of beta-catenin mRNA.

Imaging real-time gene expression in Mammalian cells with single-transcript resolution.

INTRODUCTIONThe MS2 system provides optimal sensitivity for single-molecule detection in cells. It requires two genetically encoded moieties: a reporter mRNA that contains MS2 binding site (MBS) stem loops and a fluorescent MS2 coat protein (MCP-xFP) that binds to the stem loops with high affinity, thus tagging the mRNA within the cell. This protocol describes transfection of COS-7 cells with reporter RNA (e.g., pRSV-Z-24 MBS-ß-actin) and MCP-xFP (e.g., pPolII-MCP-GFP-NLS) plasmids using calcium phosphate precipitation. The reporter mRNA plasmid must be co-transfected with the MCP-xFP-NLS plasmid for simultaneous expression in a cell. The unbound MCP-xFP-NLS is sequestered in the nucleus, leaving only the MCP-xFP-NLS that is bound to the reporter mRNA in the cytoplasm. This provides a high signal-to-noise ratio (SNR) that permits detection of single mRNA molecules. The Delta T Imaging System is used for image acquisition of fluorescent particles in the cells.

Imaging real-time gene expression in living yeast.

INTRODUCTIONThis protocol describes the application of the MS2 system to the yeast Saccharomyces cerevisiae. ASH1 mRNA tagged with six MS2 repeats (6MBSs) is used to follow the localization of the ASH1 mRNA particles to the bud tip of a haploid yeast cell. W303 yeast cells transformed with pG14-MS2-GFP and pGAL-lacZ-MS2-ASH1 are grown on select medium lacking tryptophan and leucine. RNA expression is induced by the addition of galactose, and a time-lapse movie is then acquired.

Imaging real-time gene expression in living systems with single-transcript resolution: image analysis of single mRNA transcripts.

INTRODUCTIONThis protocol describes a method for establishing a green fluorescent protein (GFP) calibration curve using dilutions of recombinant GFP and blue fluorescent beads. The total fluorescence intensity (TFI) per mRNA molecule is first calculated by imaging serial dilutions of purified enhanced GFP (eGFP) to determine the TFI within a specific volume. A calibration curve of fluorescence intensity in a given voxel per molecule of GFP is then used to determine the number of GFP molecules in the sample of formaldehyde fixed cells to be imaged. This is followed by a method for detection of single molecules in formaldehyde-fixed and live cells. These cells have been cotransfected with mRNA reporter and MCP-xFP plasmids, where MCP-xFP refers to a fluorescent protein fused to the MS2 capsid protein. It is important to collect micrographs and establish the calibration curve on the same day that the cells are imaged, using the same equipment configuration, camera settings, and image acquisition parameters.

Imaging Real-Time Gene Expression in Living Systems with Single-Transcript Resolution: Single mRNA Particle Tracking with ImageJ-Based Analysis.

INTRODUCTIONThis protocol describes the use of ImageJ software (freely available from NIH) to analyze particle dynamics in a cell using time-lapse movie frames or image stacks of fluorescent mRNA particles. Maximum intensity projections and kymographs are produced.

Imaging real-time gene expression in living systems with single-transcript resolution: construct design and imaging system setup.

INTRODUCTIONThe most common way for a cell to respond to internal and external signals is to change its gene expression pattern. This requires the synchronization of regulatory steps along the expression pathway. Biological imaging techniques can be used to visualize and measure such processes in individual live cells in real time. This article discusses the use of a fluorescent RNA-binding protein system that allows real-time analysis of gene expression with single-transcript resolution.

The structure of the myosin VI motor reveals the mechanism of directionality reversal.

Here we solve a 2.4-A structure of a truncated version of the reverse-direction myosin motor, myosin VI, that contains the motor domain and binding sites for two calmodulin molecules. The structure reveals only minor differences in the motor domain from that in plus-end directed myosins, with the exception of two unique inserts. The first is near the nucleotide-binding pocket and alters the rates of nucleotide association and dissociation. The second unique insert forms an integral part of the myosin VI converter domain along with a calmodulin bound to a novel target motif within the insert. This serves to redirect the effective 'lever arm' of myosin VI, which includes a second calmodulin bound to an 'IQ motif', towards the pointed (minus) end of the actin filament. This repositioning largely accounts for the reverse directionality of this class of myosin motors. We propose a model incorporating a kinesin-like uncoupling/docking mechanism to provide a full explanation of the movements of myosin VI.

Identification and testing of a gene expression signature of invasive carcinoma cells within primary mammary tumors.

We subjected cells collected using an in vivo invasion assay to cDNA microarray analysis to identify the gene expression profile of invasive carcinoma cells in primary mammary tumors. Expression of genes involved in cell division, survival, and cell motility were most dramatically changed in invasive cells indicating a population that is neither dividing nor apoptotic but intensely motile. In particular, the genes coding for the minimum motility machine that regulates beta-actin polymerization at the leading edge and, therefore, the motility and chemotaxis of carcinoma cells, were dramatically up-regulated. However, ZBP1, which restricts the localization of beta-actin, the substrate for the minimum motility machine, was down-regulated. This pattern of expression implicated ZBP1 as a suppressor of invasion. Reexpression of ZBP1 in metastatic cells with otherwise low levels of ZBP1 reestablished normal patterns of beta-actin mRNA targeting and suppressed chemotaxis and invasion in primary tumors. ZBP1 reexpression also inhibited metastasis from tumors. These experiments support the involvement in metastasis of the pathways identified in invasive cells, which are regulated by ZBP1.

The unique insert in myosin VI is a structural calcium-calmodulin binding site.

Myosin VI contains an inserted sequence that is unique among myosin superfamily members and has been suggested to be a determinant of the reverse directionality and unusual motility of the motor. It is thought that each head of a two-headed myosin VI molecule binds one calmodulin (CaM) by means of a single "IQ motif". Using truncations of the myosin VI protein and electrospray ionization(ESI)-MS, we demonstrate that in fact each myosin VI head binds two CaMs. One CaM binds to a conventional IQ motif either with or without calcium and likely plays a regulatory role when calcium binds to its N-terminal lobe. The second CaM binds to a unique insertion between the converter region and IQ motif. This unusual CaM-binding site normally binds CaM with four Ca2+ and can bind only if the C-terminal lobe of CaM is occupied by calcium. Regions of the MD outside of the insert peptide contribute to the Ca(2+)-CaM binding, as truncations that eliminate elements of the MD alter CaM binding and allow calcium dissociation. We suggest that the Ca(2+)-CaM bound to the unique insert represents a structural CaM, and not a calcium sensor or regulatory component of the motor. This structure is likely an integral part of the myosin VI "converter" region and repositions the myosin VI "lever arm" to allow reverse direction (minus-end) motility on actin.

A structural state of the myosin V motor without bound nucleotide.

The myosin superfamily of molecular motors use ATP hydrolysis and actin-activated product release to produce directed movement and force. Although this is generally thought to involve movement of a mechanical lever arm attached to a motor core, the structural details of the rearrangement in myosin that drive the lever arm motion on actin attachment are unknown. Motivated by kinetic evidence that the processive unconventional myosin, myosin V, populates a unique state in the absence of nucleotide and actin, we obtained a 2.0 A structure of a myosin V fragment. Here we reveal a conformation of myosin without bound nucleotide. The nucleotide-binding site has adopted new conformations of the nucleotide-binding elements that reduce the affinity for the nucleotide. The major cleft in the molecule has closed, and the lever arm has assumed a position consistent with that in an actomyosin rigor complex. These changes have been accomplished by relative movements of the subdomains of the molecule, and reveal elements of the structural communication between the actin-binding interface and nucleotide-binding site of myosin that underlie the mechanism of chemo-mechanical transduction.

An actin-dependent conformational change in myosin.

Conformational changes within myosin lead to its movement relative to an actin filament. Several crystal structures exist for myosin bound to various nucleotides, but none with bound actin. Therefore, the effect of actin on the structure of myosin is poorly understood. Here we show that the swing of smooth muscle myosin lever arm requires both ADP and actin. This is the first direct observation that a conformation of myosin is dependent on actin. Conformational changes within myosin were monitored using fluorescence resonance energy transfer techniques. A cysteine-reactive probe is site-specifically labeled on a 'cysteine-light' myosin variant, in which the native reactive cysteines were removed and a cysteine engineered at a desired position. Using this construct, we show that the actin-dependent ADP swing causes an 18 A change in distance between a probe on the 25/50 kDa loop on the catalytic domain and a probe on the regulatory light chain, corresponding to a 23 degrees swing of the light-chain domain.

Calcium functionally uncouples the heads of myosin VI.

This study examines the steady state activity and in vitro motility of single-headed (S1) and double-headed (HMM) myosin VI constructs within the context of two putative modes of regulation. Phosphorylation of threonine 406 does not alter either the rate of actin filament sliding or the maximal actin-activated ATPase rate of S1 or HMM constructs. Thus, we do not observe any regulation of myosin VI by phosphorylation within the motor domain. Interestingly, in the absence of calcium, the myosin VI HMM construct moves in an in vitro motility assay at a velocity that is twice that of S1 constructs, which may be indicative of movement that is not based on a "lever arm" mechanism. Increasing calcium above 10 microm slows both the rate of ADP release from S1 and HMM actomyosin VI and the rates of in vitro motility. Furthermore, high calcium concentrations appear to uncouple the two heads of myosin VI. Thus, phosphorylation and calcium are not on/off switches for myosin VI enzymatic activity, although calcium may alter the degree of processive movement for myosin VI-mediated cargo transport. Lastly, calmodulin mutants reveal that the calcium effect is dependent on calcium binding to the N-terminal lobe of calmodulin.