Study on the expression and mutation of human telomeric repeat binding factor (hTRF1) in 10 malignant hematopoietic cell lines

Objective： 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 ifhTRF1 mutation is one of the factors of the activation of telomerase. Methods： hTRFlcDNA 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 h TRFlmRNA in 10 cell line cells, including myelogenous leukemia cell lines K562, HL-60, U-937, NB4, THP-I, 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 ofhTRF1 in 10 cell line cells. Results： hTRF1 gene, mapped to 8q13, was divided into 10 exons and spans 38.6 kb. Four processed pseudogenes ofhTRF1 located on chromosome 13, 18, 21 and X respectively, was named as ψhTRFI-13, ψhTRFI-18, ψhTRF1-21 and ψhTRFI-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 ofintron 1, 2 and 8 ofhTRF1. Their infection on gene function is unknown and needs further studies. Conclusion： hTRF1 mutation is probably not one of the main factors for telomerase activation in malignant hematopoietic disease.

A study of the relationship between expression level of TRF1 protein and telomerase activity in human acute leukemia

Objective： To study the expression level of TRF1 （telomeric repeat binding factor 1） protein in human acute leukemia and relationship between expression level of TRF1 protein and telomerase, Methods： A quantitative Western±Blot technique was developed using anti±TRF1^33±277 monoclonal antibody and GST±TRFI purity protein as a standard to further determine the expression level of TRF1 protein in total proteins extracted from clinical specimens. Results： Bone marrow tissues of 20 acute leukemia patients were studied, 11 healthy donors＇ bone marrows were taken as a control. The expression level of TRF1 protein was significantly higher （P〈0.01） in normal bone marrow （（2.2174±0.462） μg/μl） than that of acute leukemia patients （（0.7544±0.343） μg/μl）, But there was no remarkable difference between ALL and ANLL patients （（0.6184±0.285） μg/μl vs （0.8454±0.359） μg/μl, P〉0.05）. After chemotherapy, TRFI expression level of patients with complete remission elevated （（0.7724±0.307）/μg/μl vs （1.6834±0,344）μg/μl, P〈0.01 ）, but lower than that of normal （（2.2174±0.462）/μg/μl, P〈0.01）. There was no significantly difference after chemotherapy （（0.7264±0.411） μg/μl vs （0.895±0.339） μg/μl,p〉0.05）. TRF1 expression level of patients with complete remission is higher than that of patients without complete remission （（1,683±0.344）μg/μl vs （0.895±0.339）μg/μl P〈0.01）. All samples were determined for telomerase activity. It was confirmed that the activity of telomerase in normal bone marrow was lower than that of acute leukemia patients （（0.125±0.078） μg/μl vs （0.765±0.284）μg/μl, P〈0.01）. There was no significant difference of expression level ofTRF I protein between ALL and ANLL patients （（0.897±0.290） μg/μl vs （0.677±0.268） μg/μl, P〉0.05）. After chemotherapy, telomerase activity of patients with complete remission decreased （（0.393±0.125） μg/μl）, but was still higher than that of normal （（0.125±0.078） μg/μl, P〈0.01）. Conclusion： The expression level of TRF1 protein has correlativity to the activity of telomerase （P〈0.001）.