title: A novel ARF-binding protein (LZAP) alters ARF regulation of HDM2.
abstract: The tumour suppressor ARF (alternative reading frame) is encoded by the INK4a (inhibitor of cyclin-dependent kinase 4)/ARF locus, which is frequently altered in human tumours. ARF binds MDM2 (murine double minute 2) and releases p53 from inhibition by MDM2, resulting in stabilization, accumulation and activation of p53. Recently, ARF has been found to associate with other proteins, but, to date, little is known about ARF-associated proteins that are implicated in post-translational regulation of ARF activity. Using a yeast two-hybrid screen, we have identified a novel protein, LZAP (LXXLL/leucine-zipper-containing ARF-binding protein), that interacts with endogenous ARF in mammalian cells. In the present study, we show that LZAP reversed the ability of ARF to inhibit HDM2's ubiquitin ligase activity towards p53, but simultaneously co-operated with ARF, maintaining p53 stability and increasing p53 transcriptional activity. Expression of LZAP, in addition to ARF, increased the percentage of cells in the G1 phase of the cell cycle. Expression of LZAP also caused activation of p53 and a p53-dependent G1 cell-cycle arrest in the absence of ARF. Taken together, our data suggest that LZAP can regulate ARF biochemical and biological activity. Additionally, LZAP has p53-dependent cell-cycle effects that are independent of ARF.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Jialiang
authors.initials: J
authors.lastname: Wang
authors.forename: Xiaping
authors.initials: X
authors.lastname: He
authors.forename: Ying
authors.initials: Y
authors.lastname: Luo
authors.forename: Wendell G
authors.initials: WG
authors.lastname: Yarbrough
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D011485:Protein Binding; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin / Q000378:metabolism
chemical_list: C452880:Atp5md protein, rat; C405928:CDK5RAP3 protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2