Human PinX1 mediates TRF1 accumulation in nucleolus and enhances TRF1 binding to telomeres.
Human PinX1 (hPinX1) is known to interact with telomere repeat binding factor 1 (TRF1) and telomerase. Here, we report that hPinX1 regulates the nucleolar accumulation and telomeric association of TRF1. In HeLa, HA-hPinX1 was co-localized with fibrillarin, a nucleolar protein, in 51% of the transfected cells and was present in the nucleoplasm of the remaining 48%. Mutant analysis showed that the C-terminal region was important for nucleolar localization, while the N-terminus exhibited an inhibitory effect on nucleolar localization. Unlike HA- and Myc-hPinX1, GFP-hPinX1 resided predominantly in the nucleolus. Nuclear hPinX1 bound to telomeres and other repeat sequences as well but, despite its interaction with TRF1, nucleolar hPinX1 did not bind to telomeres. Nucleolar hPinX1 forced endogenous TRF1 accumulation in the nucleolus. Furthermore, TRF1 binding to telomeres was upregulated in cells over-expressing hPinX1. In an ALT cell line, WI-38 VA-13, TRF1 did not co-localize with hPinX1 in the nucleoli. In summary, hPinX1 likely interacts with TRF1 in both the nucleolus and the nucleoplasm, and excess hPinX1 results in increased telomere binding of TRF1. The PinX1 function of mediating TRF1 nucleolar accumulation is absent from ALT cells, suggesting that it might be telomerase-dependent.
Yoo
Jeong Eun
JE
Department of Pathology, Institute of Gastroenterology, Center for Chronic Metabolic Disease, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea.
Oh
Bong-Kyeong
BK
Park
Young Nyun
YN
D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016615:Telomere / Q000378:metabolism*; D035321:Telomeric Repeat Binding Protein 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; C440808:PINX1 protein, human; D011993:Recombinant Fusion Proteins; D035321:Telomeric Repeat Binding Protein 1; D025521:Tumor Suppressor Proteins