The Insertion in Fingers Domain in Human Telomerase Can Mediate Enzyme Processivity and Telomerase Recruitment to Telomeres in a TPP1-Dependent Manner.
In most human cancer cells, cellular immortalization relies on the activation and recruitment of telomerase to telomeres. The telomere-binding protein TPP1 and the TEN domain of the telomerase catalytic subunit TERT regulate telomerase recruitment. TERT contains a unique domain, called the insertion in fingers domain (IFD), located within the conserved reverse transcriptase domain. We report the role of specific hTERT IFD residues in the regulation of telomerase activity and processivity, recruitment to telomeres, and cell survival. One hTERT IFD variant, hTERT-L805A, with reduced activity and processivity showed impaired telomere association, which could be partially rescued by overexpression of TPP1-POT1. Another previously reported hTERT IFD mutant enzyme with similarly low levels of activity and processivity, hTERT-V791Y, displayed defects in telomere binding and was insensitive to TPP1-POT1 overexpression. Our results provide the first evidence that the IFD can mediate enzyme processivity and telomerase recruitment to telomeres in a TPP1-dependent manner. Moreover, unlike hTERT-V791Y, hTERT-V763S, a variant with reduced activity but increased processivity, and hTERT-L805A, could both immortalize limited-life-span cells, but cells expressing these two mutant enzymes displayed growth defects, increased apoptosis, DNA damage at telomeres, and short telomeres. Our results highlight the importance of the IFD in maintaining short telomeres and in cell survival.
Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Canada Division of Experimental Medicine, McGill University, Montréal, Canada.
Tsz Wai
TW
Chu
Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Canada Department of Anatomy and Cell Biology, McGill University, Montréal, Canada.
Yasmin
Y
D'Souza
Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Canada Division of Experimental Medicine, McGill University, Montréal, Canada Department of Anatomy and Cell Biology, McGill University, Montréal, Canada chantal.autexier@mcgill.ca.
Chantal
C
Autexier
D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D004249:DNA Damage / Q000502:physiology; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D057057:Serine Proteases / Q000378:metabolism*; D000089804:Shelterin Complex / Q000235:genetics* / Q000378:metabolism; D019098:Telomerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000201:enzymology* / Q000235:genetics*; D059506:Telomere Shortening / Q000502:physiology; D034501:Telomere-Binding Proteins / Q000235:genetics* / Q000378:metabolism
C495876:ACD protein, human; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; C509186:TERT protein, human; D019098:Telomerase; D057057:Serine Proteases; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases