title: Proline-rich acidic protein 1 (PRAP1) is a novel interacting partner of MAD1 and has a suppressive role in mitotic checkpoint signalling in hepatocellular carcinoma.
abstract: Loss of mitotic checkpoint of cells contributes to chromosomal instability and leads to carcinogenesis. Mitotic arrest deficient 1 (MAD1) is a key component in mitotic checkpoint signalling. In this study, we identified a novel MAD1 interacting partner, proline-rich acidic protein 1 (PRAP1), using yeast-two hybrid screening, and investigated its role in mitotic checkpoint signalling in hepatocellular carcinoma (HCC). We demonstrated the physical interaction of PRAP1 with MAD1 and of PRAP1 with MAD1 isoform MAD1β, using a co-immunoprecipitation assay. Moreover, stable expression of PRAP1 in mitotic checkpoint-competent HCC cells, BEL-7402 and SMMC-7721, induced impairment of the mitotic checkpoint (p < 0.01), formation of chromosome bridges (p < 0.01) and aberrant chromosome numbers (p < 0.001). Interestingly, ectopic expression PRAP1 in HCC cells led to significant under-expression of MAD1. In human HCC tumours, 40.4% (23/57) of HCCs showed under-expression of PRAP1 protein as compared with their corresponding non-tumorous livers; up-regulation of MAD1 protein was significantly associated with down-regulation of PRAP1 (p = 0.030). Our data revealed that PRAP1 is a protein interacting partner of MAD1 and that PRAP1 is able to down-regulate MAD1 and suppress mitotic checkpoint signalling in HCC.
authors.affiliation: State Key Laboratory for Liver Research, University of Hong Kong; Department of Pathology, University of Hong Kong.
authors.forename: Karen Man-Fong
authors.initials: KM
authors.lastname: Sze
authors.forename: Glanice Kin-Yan
authors.initials: GK
authors.lastname: Chu
authors.forename: Queenie Ho-Yan
authors.initials: QH
authors.lastname: Mak
authors.forename: Joyce Man-Fong
authors.initials: JM
authors.lastname: Lee
authors.forename: Irene Oi-Lin
authors.initials: IO
authors.lastname: Ng
mesh_terms: D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002869:Chromosome Aberrations; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047468:Immunoprecipitation; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D008938:Mitosis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011257:Pregnancy Proteins / Q000235:genetics / Q000378:metabolism*; D025941:Protein Interaction Mapping; D015398:Signal Transduction; D014162:Transfection; D020798:Two-Hybrid System Techniques; D055815:Young Adult
chemical_list: D018797:Cell Cycle Proteins; C501384:MAD1L1 protein, human; D009687:Nuclear Proteins; D011257:Pregnancy Proteins; C581328:proline-rich acidic protein 1, human
keywords: MAD1; chromosomal instability; hepatocellular carcinoma; mitotic checkpoint; proline-rich acidic protein 1; protein interactions