ABSTRACT
More than 200 assembly factors (AFs) are required for the production of ribosomes in yeast. The stepwise association and dissociation of these AFs with the pre-ribosomal subunits occurs in a hierarchical manner to ensure correct maturation of the pre-rRNAs and assembly of the ribosomal proteins. Although decades of research have provided a wealth of insights into the functions of many AFs, others remain poorly characterized. Pol5 was initially classified with B-type DNA polymerases, however, several lines of evidence indicate the involvement of this protein in ribosome assembly. Here, we show that depletion of Pol5 affects the processing of pre-rRNAs destined for the both the large and small subunits. Furthermore, we identify binding sites for Pol5 in the 5' external transcribed spacer and within domain III of the 25S rRNA sequence. Consistent with this, we reveal that Pol5 is required for recruitment of ribosomal proteins that form the polypeptide exit tunnel in the LSU and that depletion of Pol5 impairs the release of 5' ETS fragments from early pre-40S particles. The dual functions of Pol5 in 60S assembly and recycling of pre-40S AFs suggest that this factor could contribute to ensuring the stoichiometric production of ribosomal subunits.
Subject(s)
DNA-Directed DNA Polymerase/genetics , Protein Biosynthesis , RNA, Ribosomal/genetics , Ribosome Subunits, Large, Eukaryotic/genetics , Ribosome Subunits, Small, Eukaryotic/genetics , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae/genetics , Amino Acid Sequence , Binding Sites , DNA-Directed DNA Polymerase/chemistry , DNA-Directed DNA Polymerase/metabolism , Models, Molecular , Nucleic Acid Conformation , Protein Binding , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , RNA Precursors/chemistry , RNA Precursors/genetics , RNA Precursors/metabolism , RNA, Ribosomal/chemistry , RNA, Ribosomal/metabolism , Ribosome Subunits, Large, Eukaryotic/metabolism , Ribosome Subunits, Large, Eukaryotic/ultrastructure , Ribosome Subunits, Small, Eukaryotic/metabolism , Ribosome Subunits, Small, Eukaryotic/ultrastructure , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae Proteins/chemistry , Saccharomyces cerevisiae Proteins/metabolism , Sequence Alignment , Sequence Homology, Amino Acid , ThermodynamicsABSTRACT
PURPOSE: To compare the results of treadmill exercise testing (TM) to arm-leg ergometry testing (AL) in patients with peripheral arterial disease (PAD). METHODS: Twelve men and 8 women with PAD (mean age, 62 +/- 10 years) completed a treadmill test and an arm-leg ergometer exercise test. Oxygen uptake, heart rate, rate-pressure product (x10(-3)), ratings of claudication and perceived exertion, and power were measured. RESULTS: Peak oxygen uptake, heart rate, and rate-pressure product were similar between TM and AL. Exercise duration was longer and the peak power higher on the AL than on the TM. Claudication pain > or =3/4 was the reason for test termination in all subjects during TM test and in 13 subjects during AL. Nine patients discontinued due to severe claudication on both tests, but the pain occurred later in AL than TM. CONCLUSIONS: Although peak oxygen uptake was similar between the 2 exercise tests, patients with PAD exercised longer and to a higher peak power during the AL. These data suggest that the AL test may be used to evaluate peak exercise capacity in patients with PAD. The AL may also provide an alternate method for detecting PAD and coronary heart disease.
Subject(s)
Arm , Arterial Occlusive Diseases/physiopathology , Exercise Test , Exercise Tolerance , Leg , Peripheral Vascular Diseases/physiopathology , Aged , Arm/blood supply , Arm/physiopathology , Blood Pressure , Exercise Test/classification , Female , Heart Rate , Humans , Intermittent Claudication/physiopathology , Leg/blood supply , Leg/physiopathology , Male , Middle Aged , Oxygen ConsumptionABSTRACT
PURPOSE: Although the Peripheral Arterial Disease Rehabilitation Program (PADRx) improves walking ability and quality of life over brief periods of follow-up, the long-term durability of results has not been established. This study examined functional status, walking ability, and quality of life in patients several months after completion of a 12-week PADRx. METHODS: Patients who completed a PADRx were eligible for participation. A Medical Outcomes Study 36-Item Short Form (SF-36), Walking Impairment Questionnaire (WIQ), and physical activity questionnaire were administered by telephone. A progressive treadmill test was performed on-site. RESULTS: Of 63 eligible patients, 14 were lost to follow-up, 11 refused participation, and four died. Thirty-four patients had completed PADRx 20 to 80 months previously (mean, 48.2 +/- 13.7 months), and completed the phone survey. Fifteen patients reported exercising a minimum of 60 min/wk for 3 months (EX group), and 19 had not exercised in the preceding 3 months (SED group). Self-reported SF-36 values were significantly different between the EX and SED groups for Physical Function (43.3 +/- 8.2 vs 34.2 +/- 7.8), Role-Physical Function (41.2 +/- 7.7 vs 32.8 +/- 9.2), and Bodily Pain (46.9 +/- 8.8 vs 38.9 +/- 7.1), as well as the Physical Composite (43.5 +/- 6.5 vs 34.0 vs 5.8) domains of the SF-36. Similarly the WIQ demonstrated significant differences in Walking Distance (46.8 +/- 36.2 vs 7.8 +/- 9.4), Walking Speed (47.5 +/- 32.6 vs 14.5 +/- 13.9), and Stair Climbing (60.6 +/- 36.6 vs 37.1 +/- 27.6), favoring the EX group. Sixteen patients, equally distributed between the EX and SED groups, completed the progressive treadmill test. Both groups had experienced improvement (P <.05) in claudication pain time and maximal walking time after completing the 12-week supervised program. The EX group maintained increased claudication pain time of 121% and maximum walking time of 109% over baseline, whereas the SED group values had returned to baseline (P <.05). CONCLUSIONS: Patients with claudication realize symptomatic and functional improvement with supervised exercise programs. Those who continue to exercise will potentially maintain these benefits and experience improved health-related quality of life.
