C-terminal regions of the human telomerase catalytic subunit essential for in vivo enzyme activity.
Most human cancer cells are thought to acquire the ability to divide beyond the capacity of normal somatic cells through illegitimately activating the gene hTERT, which encodes the catalytic subunit of telomerase. While telomerase reverse transcriptase (TERT) is conserved in most eukaryotes, mounting evidence suggests that the C terminus of the human protein may have functions unique to higher eukaryotes. To search for domains responsible for such functions, we assayed a panel of tandem substitution mutations encompassing this region of human TERT for in vitro and in vivo functionality. We found four clusters of mutations that inactivated the biochemical and biological functions of telomerase, separated by mutations that had little or no effect on enzyme activity. We also identified a region where mutations generate catalytically active but biologically inert proteins. This C-terminal region that dissociates activities of telomerase (C-DAT) does not appear to be involved in nuclear localization or protein multimerization. Instead, it appears that the C-DAT region is involved in a step of in vivo telomere synthesis after the assembly of a catalytically active enzyme. Intriguingly, all of the described regions reside in a portion of TERT that is dispensable for cellular viability in yeast, arguing for a divergent role of the C terminus in higher eukaryotes.
Banik
Soma S R
SS
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Guo
Chuanhai
C
Smith
Allyson C
AC
Margolis
Seth S
SS
Richardson
D Ashley
DA
Tirado
Carlos A
CA
Counter
Christopher M
CM
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D029681:Arabidopsis Proteins / Q000737:chemistry; D002384:Catalysis; D020134:Catalytic Domain; D002460:Cell Line; D016384:Consensus Sequence; D004268:DNA-Binding Proteins; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013329:Structure-Activity Relationship; D019098:Telomerase / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D016615:Telomere / Q000378:metabolism
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C509186:TERT protein, human; D019098:Telomerase; C509187:Tert protein, mouse