Article Abstract:
Tumor progression reactivates the telomeres elongating ribonucleoprotein enzyme telomerase repressed in human somatic cells. The human hEST2 gene, which has a similar sequence with lower eukaryote telomerase catalytic subunit genes, has been cloned. hEST2 was not found in telomerase-negative cell lines but was dominant in cancer cell lines, tumors and telomerase positive tissues. Results show that telomerase activation during tumor progression and cellular immortalization requires the induction of hEST2 mRNA expression.
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Article Abstract:
Est1p, a protein coded by the protein, EST1, may be a subunit of yeast telomerase or else it is a protein associated with telomerase that is necessary for its activity in vitro. Telomerase is a ribonucleoprotein that uses an RNA template in the absence of a DNA template to increase the telomeric DNA strand. Telomerases are necessary for the maintenance of Saccharomyces chromosomes and their function is to prevent loss of DNA that would occur if a linear DNA molecule were replicated by a DNA polymerase.
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Article Abstract:
Analyses of the sequences of various ataxia telangiectasia mutated (ATM)-like genes for homology reveals that the Saccharomyces TEL1 gene is the closest homolog of the ATM gene while the drosophila mei-41 gene, the Saccharomyces MEC1 gene, and the S. pombe rad3 gene share a high degree of structural and functional similarity to ATM. The human DNA-dependent protein kinase, DNA-PK is discussed.
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