title: Retinoic acid regulates the expression of PBX1, PBX2, and PBX3 in P19 cells both transcriptionally and post-translationally.
abstract: Pre-B cell leukemia transcription factors (PBXs) are important co-factors for the transcriptional regulation mediated by a number of Hox proteins during embryonic development. It was previously shown that the expression of several Pbx genes is elevated in mouse embryo limb buds and embryonal carcinoma P19 cells upon retinoic acid (RA) treatment although the mechanism of this induction is not well understood. In this report, we demonstrate that PBX1a, PBX1b, PBX2, and PBX3 mRNAs and PBX1/2/3 proteins are induced during endodermal and neuronal differentiation of P19 cells in a RAR-dependent subtype-unspecific manner following RA treatment. The increases in both PBX1 mRNA and PBX3 mRNA levels are secondary responses to RA treatment requiring new proteins synthesis while the increase in PBX2 mRNA is a primary response. The RA-dependent increases in PBX1 mRNA, PBX2 mRNA, and PBX3 mRNA levels are likely to be transcriptionally regulated since the stability of these mRNAs does not change. In addition, the half-lives of PBX1/2/3 proteins are significantly extended by RA treatment. Two possible mechanisms could contribute to the stabilization of PBX proteins: PBX proteins associate with RA-dependent increased levels of MEIS proteins, and RA may decrease the proteasome dependent degradation of PBX proteins.
authors.affiliation: Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
authors.forename: Pu
authors.initials: P
authors.lastname: Qin
authors.forename: Juliet M
authors.initials: JM
authors.lastname: Haberbusch
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Soprano
authors.forename: Dianne Robert
authors.initials: DR
authors.lastname: Soprano
mesh_terms: D000818:Animals; D018236:Carcinoma, Embryonal / Q000378:metabolism; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D020871:RNA Stability; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014212:Tretinoin / Q000494:pharmacology* / Q000502:physiology; D015854:Up-Regulation / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; C481797:Pbx1 protein, mouse; C490382:Pbx2 protein, mouse; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; C090466:proto-oncogene protein Pbx3; D014212:Tretinoin; D046988:Proteasome Endopeptidase Complex