Important role of Ser 219 phosphorylation of TRF1 in regulation of cell cycle / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the role of Ser 219 phosphorylation of TRF1 (telomere repeat binding factor 1) in regulation of cell cycle.</p><p><b>METHODS</b>The mimicking phosphorylation mutant (TRF1S219D-GFP) and the non-phosphorylatable mutant (TRF1S219A-GFP) were constructed; the mutant genes and corresponding proteins were checked by sequencing and Western blot, respectively. Immunofluorescence staining was performed to detect the localization of mutants in HeLa cells. Cell cycle was analyzed by flow cytometry and ATM level was evaluated by immunoblotting.</p><p><b>RESULTS</b>The mutant genes were verified by direct sequencing and protein expression of GFP-tagged mutants was confirmed by immunoblotting.TRF1S219A-GFP and TRF1S219D-GFP were both localized in telomere of HeLa cells. Moreover, overexpression of TRF1-GFP or TRF1S219A-GFP resulted in an accumulation of HeLa cells in G2/M (P<0.05). The protein level of ATM was increased when overexpression the wide type or mutants.</p><p><b>CONCLUSION</b>The Ser 219 phosphorylation of TRF1 by ATM could result in cell cycle arrest in G2/M, which is related to overexpression of TRF1.</p>

Localization of p53(301-393) mutant and its effect on mitosis / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To observe the localization of p53(301-393)(residues 301-393) in p53 positive/negative cells and its effect on cell mitosis.</p><p><b>METHODS</b>The protein expression of p53-GFP and p53(301-393)-GFP was checked by immunoblotting after transfection. Immunofluorescence staining was performed to detect the localization of wide type and mutant in Hela cells (p53 positive) and H1299 cells (p53 negative). The cell morphology of H1299 cells transfected of p53(301-393)-GFP and the cells in mitotic phase were observed. Cell cycle was analyzed by flow cytometry and p53 protein level in HeLa cells was evaluated by Western blot after transfection of p53-GFP and p53(301-393)-GFP.</p><p><b>RESULTS</b>The protein expression of p53-GFP and p53(301-393)-GFP was verified, p53-GFP was about 90 kMr and p53(301-393)-GFP about 40 kMr. Immunofluorescence microscopy demonstrated that both proteins were diffusely located in the nuclei of HeLa cells and H1299 cells. But different from the p53-GFP, the p53(301-393)-GFP was distributed in the nucleolus of HeLa cells. After transfection of the two plasmids, mitosis was inhibited in H1299 cells and some cells underwent apoptosis. G2/M progression of HeLa cells could be blocked by transfection of p53(301-393)-GFP, but endogenous p53 protein level was not changed.</p><p><b>CONCLUSION</b>p53(301-393)has a different localization in the p53 positive and p53 negative cells and could inhibit mitosis and cause the cell cycle arrest in G2/M.</p>

Interaction between a novel centrosomal protein TACP1 and mitotic kinase Nek2A / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To study interaction between a novel centrosomal protein TACP1 and mitotic kinase Nek2A.</p><p><b>METHODS</b>Nek2A305-446 protein was expressed and purified in E.coli and TACP1 protein was expressed in transfected 293T cells. Pull-down assay was used to examine the interaction between Nek2A305-446 and TACP1. TACP1 and Nek2A complex was tested by co-immunoprecipitation assay with polyclonal anti-TACP1 antibody. The localization of those two proteins in Hela cells was verified by immunofluorescence.</p><p><b>RESULTS</b>TACP1 was pulled down by Nek2A305-446 protein but not by GST control. Nek2A was co-precipitated with TACP1 protein by polyclonal anti-TACP1 antibody but not by pre-immunization serum. The Immunofluorescence test showed that these two proteins formed a complex at centrosome during mitosis.</p><p><b>CONCLUSION</b>Centrosomal protein TACP1 is a novel interacting protein with Nek2A, both of which are localized in centrosome during mitosis.</p>

Study on the expression and mutation of human telomeric repeat binding factor (hTRF1) in 10 malignant hematopoietic cell lines / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

<p><b>OBJECTIVE</b>Detecting the expression and mutation of human telomeric repeat binding factor (hTRF1) in 10 malignant hematopoietic cell line cells on the base of determining its genomic structure and its four pseudogenes to clarify if hTRF1 mutation is one of the factors of the activation of telomerase.</p><p><b>METHODS</b>hTRF1cDNA sequences were obtained from GenBank, its genome structure and pseudogenes were forecasted by BLAST and other biology information programs and then testified by sequencing. Real-time RT-PCR was used to detect the expression of hTRF1mRNA in 10 cell line cells, including myelogenous leukemia cell lines K562, HL-60, U-937, NB4, THP-1, HEL and Dami; lymphoblastic leukemia cell lines 6T-CEM, Jurkat and Raji. Telomerase activities of cells were detected by using telomeric repeat amplification (TRAP)-ELISA protocol. PCR and sequencing were used to detect mutation of each exon of hTRF1 in 10 cell line cells.</p><p><b>RESULTS</b>hTRF1 gene, mapped to 8q13, was divided into 10 exons and spans 38.6 kb. Four processed pseudogenes of hTRF1 located on chromosome 13, 18, 21 and X respectively, was named as PsihTRF1-13, PsihTRF1-18, PsihTRF1-21 and PsihTRF1-X respectively. All cell line cells showed positive telomerase activity. The expression of hTRF1 was significantly lower in malignant hematopoietic cell lines cells (0.0338, 0.0108-0.0749) than in normal mononuclear cells (0.0493, 0.0369-0.128) (P=0.004). But no significant mutation was found in all exons of hTRF1 in 10 cell line cells. Four variants were found in part of intron 1, 2 and 8 of hTRF1. Their infection on gene function is unknown and needs further studies.</p><p><b>CONCLUSION</b>hTRF1 mutation is probably not one of the main factors for telomerase activation in malignant hematopoietic disease.</p>

Localization of human telomere repeat binding factor 1 in telomerase-positive and-negative cells and its expression during cell cycle / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To observe the distribution pattern of human telomere repeat binding factor 1(TRF1) in the telomerase-positive (HeLa) and telomerase-negative cells (WI38-2RA) and to investigate its expression level during the cell cycle.</p><p><b>METHODS</b>The full-length sequences of TRF1(TRF1FL) and its mutant with N and C terminus deletion (TRF1DeltaNC) were generated by PCR amplification, the resulting fragments were cloned into pEGFP-C2 mammalian expression vector. GFP-tagged proteins were verified by Western blotting with rabbit anti-TRF1 and mouse anti-GFP antibodies after cell transfection. Immunofluorescence staining were performed to detect the TRF1 localization in HeLa and WI38-2RA cells. Metaphase spreads from HeLa cells were also prepared to observe TRF1 localization in chromosomes. HeLa cells were arrested by thymidine and nocodazole at different cell stages. Cell cycles were analyzed by flow cytometry and TRF1 levels were evaluated by semi-quantitative Western blotting.</p><p><b>RESULTS</b>TRF1FL and TRF1PNC fragments were sized about 1.3 kb and 0.95 kb. GFP-tagged TRF1FL and TRF1DeltaNC proteins were 80 kD and 60 kD, respectively. In both HeLa and WI38-2RA cells, TRF1FL had a speckled distribution in the nuclei,however, TRF1FL did not coincide with promyelocytic leukemia (PML) nuclear body in HeLa cells while it exclusively did in WI38-2RA cells. Moreover, TRF1FL was exactly localized at the termini of metaphase spreads in HeLa cells. In contrast, TRF1PNC was diffusely distributed throughout the nuclei. Analysis by semi-quantitative Western blotting indicated that TRF1 levels increased with cell cycle progression, which reached the zenith at the M phase and went down to the nadir at G1/S point. The TRF1 level at M phase was about 3.9 times than that at G1/S point(t=12.92iP<0.01).</p><p><b>CONCLUSION</b>TRF1 has a different localization in telomerase-positive and telomerase-negative cells, which suggests TRF1 might exert different functions in these cells. TRF1 level is regulated with cell cycle.</p>

Telomerase activity of human bone marrow mesenchymal stem cells / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the telomerase activity in mesenchymal stem cells (hMSCs) from human bone marrow after their in vitro committed differentiation into adipocytes and cryopreservation.</p><p><b>METHODS</b>hMSCs were isolated from human bone marrow. The isolated hMSCs were induced to differentiate into adipocytes in vitro or cryopreserved. TRAP assay (telomerase repeat amplification protocol assay) was employed to detect telomerase activity in those hMSCs.</p><p><b>RESULTS</b>Telomerase activity (RTA) in hMSCs (n=19) was (1.46 +/-0.67)%, while that in hMSCs-derived adipocytes (n=3) was (11.80 +/-2.52)% (P<0.001). RTA of hMSCs-passage 1.3 (n=10) was (1.46+/-0.83)%, and that of hMSCs-passage 4-7(n=9) was (1.46 +/-0.47)% (P=0.99). Cryopreservation did not affect the telomerase activity in hMSCs, RTA of fresh hMSCs (n=13) was (1.41 +/-0.44)%, RTA of frozen hMSCs (n=6) was (1.57 +/-1.07)% (P=0.64).</p><p><b>CONCLUSION</b>hMSCs are telomerase-negative, but telomerase activity in hMSCs-derived adipocytes is upregulated.</p>

Isolation of Tara protein and its gene cloning / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To isolate and identify TRF1 immunoprecipitating protein complex and to clone the candidate gene.</p><p><b>METHODS</b>The co-immunoprecipitation assay was employed to isolate TRF1 protein complex and the immunoprecipitate was subjected to MALDI-TOF mass spectrometry for protein identification. The candidate gene was amplified by temperature-gradient PCR from human testis cDNA library and then cloned into pEGFP-C2 vector for eukaryotic expression. The amplified gene was verified by direct sequencing and GFP-tagged protein was confirmed by immunoblotting.</p><p><b>RESULTS</b>Tara protein with the size of 68 kD was identified from the TRF1 precipitate. The candidate gene amplified from cDNA library was about 1.7 kb as expected. Sequencing demonstrated the amplified fragment had 99.9% of homogenesis with Tara CDS sequence (gi:30474869). GFP-tagged fusion protein was about 100 kD. Tara was diffusely distributed in cytoplasm at interphase and in whole cells at mitotic phase.</p><p><b>CONCLUSION</b>Tara might be an interacting protein with TRF1. However, further investigation would be required to confirm if they were bona fide partners.</p>

Expression of human telomere repeat binding factor 1 (TRF1) in acute leukemia cells and its correlation with telomerase activities / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To study the expression of human telomere repeat binding factor 1 (TRF1) to investigate the correlation of telomerase activity with acute leukemia.</p><p><b>METHODS</b>Leukemic cells were collected from 30 cases of acute leukemia. Realtime quantitative PCR with fluorescence probe hybridization was used to measure expression of TRF1 and hTERT mRNA in leukemic cells.</p><p><b>RESULTS</b>TRF1 mRNA expression was 0.0126 (0.0127-0.0546) in acute non-lymphocytic leukemia (ANLL), which was lower than that in normal mononuclear cells [0.0457 (0.00839-0.262), P<0.001], but its expression in acute lymphoblastic leukemia (ALL) cells [0.0745 (1.92 x 10(-6)-0.193)] had no significant difference compared with that in normal mononuclear cells. TRF1 expression in ANLL cells was significantly lower than that in ALL cells (P=0.001). The expressions of TRF1 mRNA in AL cells and normal mononuclear cells had no significant correlation with expression of hTERT mRNA (r=-0.173, P=0.207).</p><p><b>CONCLUSION</b>The expression of TRF1 is lower in ANLL cells, which indicates TRF1 may have some effect on telomerase activity by regulating telomere length in ANLL cells.</p>

Expression of Pin1 in malignant hematopoietic cells and its relation with cell cycle / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To study the expression of peptidyl-prolyl cis/trans isomerase (PPIase or Pin1) in malignant hematopoietic cells and its relation with cell cycle.</p><p><b>METHODS</b>Realtime quantitative PCR with fluorescence probe hybridization was used to measure expression of Pin1 mRNA in malignant hematopoietic cell lines and normal mononuclear cells separated from bone marrow. HeLa cells were blocked with Thymidine and Nocodazole in different cell phases and then the expression of Pin1 mRNA and protein were detected by realtime-PCR and immunoblotting.</p><p><b>RESULTS</b>The expression of Pin1 in malignant hematopoietic cell lines was significantly higher than that in normal controls (0.339 +/-0.093 compared with 0.038 +/-0.005, P<0.01). Its expression in myeloid malignant hematopoietic cell lines was significantly higher than that in normal controls (0.388 +/-0.115 compared with 0.038 +/-0.005, P<0.01) and so was the malignant lymphocytic cell lines (0.226 +/-0.166 compared with 0.038 +/-0.005, P<0.01). The expression of Pin1 was closely correlated with cell cycle. It was the highest in G1 phase and the lowest in S phase (110.762 +/-16.737 compared with 4.080 +/-0.634, P<0.01).</p><p><b>CONCLUSION</b>Pin1 is overexpressed in malignant hematopoietic cell lines and its expression is different during cell cycle that is highest in G1 phase and lowest in S phase.</p>