Telomeric function of mammalian telomerases at short telomeres.
Telomerase synthesizes telomeric sequences and is minimally composed of a reverse transcriptase (RT) known as TERT and an RNA known as TR. We reconstituted heterologous mouse (m) and human (h) TERT-TR complexes and chimeric mTERT-hTERT-hTR complexes in vitro and in immortalized human alternative lengthening of telomere (ALT) cells. Our data suggest that species-specific determinants of activity, processivity and telomere function map not only to the TR but also to the TERT component. The presence of hTERT-hTR, but not heterologous TERT-TR complexes or chimeric mTERT-hTERT-hTR complexes, significantly reduced the percentage of chromosomes without telomeric signals in ALT cells. Moreover, heterologous and chimeric complexes were defective in recruitment to telomeres. Our results suggest a requirement for several hTERT domains and interaction with multiple proteins for proper recruitment of telomerase to the shortest telomeres in human ALT cells. Late-passage mTERT(-/-) mouse embryonic stem (ES) cells ectopically expressing hTERT or mTERT harboured fewer chromosome ends without telomeric signals and end-to-end fusions than typically observed in late-passage mTERT(-/-) ES cells. The ability of hTERT to function at mouse telomeres and the inability of mTERT to function at human telomeres suggest that mechanisms regulating the recruitment and activity of hTERT at mouse telomeres might be less stringent than the mechanisms regulating mTERT at human telomeres.
Fakhoury
Johans
J
Bloomfield Center for Research in Aging, Lady Davis Institute, Jewish General Hospital, 3755 Côte Ste-Catherine Road, Montreal QC, Canada H3T 1E2.
Marie-Egyptienne
Delphine Tamara
DT
Londoño-Vallejo
José-Arturo
JA
Autexier
Chantal
C
D000818:Animals; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D004247:DNA / Q000096:biosynthesis*; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D051379:Mice; D055503:Protein Multimerization; D013045:Species Specificity; D013379:Substrate Specificity; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes / Q000235:genetics
D004247:DNA; C509186:TERT protein, human; D019098:Telomerase; C509187:Tert protein, mouse