title: Characterization of the promoter region of TCblR/CD320 gene, the receptor for cellular uptake of transcobalamin-bound cobalamin.
abstract: Cellular uptake of cobalamin (Cbl) is mediated by the transcobalamin receptor (TCblR) that binds and internalizes transcobalamin (TC) saturated with Cbl. These receptors are expressed in actively proliferating cells and are down-regulated in quiescent cells. The 5' region of TCblR gene was analyzed for promoter activity to determine transcriptional regulation of TCblR expression. The region -668 to -455 appears to regulate TCblR expression. We have identified transcription factors MZF-1 (myeloid zinc finger 1)/RREB-1 (Ras-responsive element binding protein 1), C/EBP (CCAAT/enhancer binding protein)/HNF-3beta (hepatocyte nuclear factor 3) and AP-1(activator protein 1) as proteins likely to be involved in this regulation with the former region primarily involved in up regulation and the latter two regions involved in suppression of TCblR expression. These transcription factors are involved in cell proliferation and differentiation. Thus the cell cycle associated expression of TCblR appears to be tightly regulated in synchrony with the proliferative phase of the cell cycle.
authors.affiliation: School of Graduate Studies, SUNY-Downstate Medical Center, Brooklyn, NY 11203, USA.
authors.forename: Wenxia
authors.initials: W
authors.lastname: Jiang
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Sequeira
authors.forename: Yasumi
authors.initials: Y
authors.lastname: Nakayama
authors.forename: Shao-Chiang
authors.initials: SC
authors.lastname: Lai
authors.forename: Edward V
authors.initials: EV
authors.lastname: Quadros
mesh_terms: D015703:Antigens, CD / Q000235:genetics*; D001483:Base Sequence; D002453:Cell Cycle; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014155:Transcobalamins / Q000378:metabolism; D014157:Transcription Factors; D014805:Vitamin B 12 / Q000235:genetics
chemical_list: D015703:Antigens, CD; C538894:CD320 protein, human; D011956:Receptors, Cell Surface; D014155:Transcobalamins; D014157:Transcription Factors; C028176:transcobalamin receptor; D014805:Vitamin B 12