DNA-protein kinase catalytic subunit-interacting protein KIP binds telomerase by interacting with human telomerase reverse transcriptase.
Telomere homeostasis, a process that is essential for continued cell proliferation and genomic stability, is regulated by endogenous telomerase and a collection of associated proteins. In this paper, a protein called KIP (previously reported as a protein that binds specifically to DNA-dependent protein kinase), has been identified as a telomerase-regulating activity based on the following pieces of evidence. First, complexes between KIP and the catalytic subunit of telomerase (hTERT) were identified using the yeast two-hybrid technique. Second, antibodies specific to KIP immunoprecipitate human telomerase in cell-free extracts. Third, immunolocalization experiments demonstrate that KIP is a nuclear protein that co-localizes with hTERT in cells. Fourth, KIP binds to hTERT both in vitro and in vivo in the absence of human telomerase RNA or telomeric DNA, thus defining the catalytic subunit of telomerase as the site of physical interaction. Fifth, co-immunoprecipitation experiments suggest that KIP-hTERT complexes form readily in cells and that overexpression of KIP in telomerase-positive cells increases endogenous telomerase activity. Finally, continued overexpression of KIP (60 population doublings) resulted in cells with elongated telomeres; thus, KIP directly or indirectly stimulates telomerase activity through hTERT and contributes to telomere lengthening. The collective data in this paper suggest that KIP plays a positive role in telomere length maintenance and/or regulation and may represent a novel target for anti-cancer drug development.
Lee
Gun Eui
GE
Department of Biology and Molecular Aging Research Center, Yonsei University, 134 Shinchon-dong, Seoul 120-749, Korea.
Yu
Eun Young
EY
Cho
Chae Hyun
CH
Lee
Junho
J
Muller
Mark T
MT
Chung
In Kwon
IK
D000970:Antineoplastic Agents / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D002455:Cell Division; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008957:Models, Genetic; D009687:Nuclear Proteins; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry*; D019098:Telomerase / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D000970:Antineoplastic Agents; C109198:CIB1 protein, human; D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D005982:Glutathione Transferase; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D019098:Telomerase