title: Stem-loop binding protein, the protein that binds the 3' end of histone mRNA, is cell cycle regulated by both translational and posttranslational mechanisms.
abstract: The expression of the replication-dependent histone mRNAs is tightly regulated during the cell cycle. As cells progress from G(1) to S phase, histone mRNA levels increase 35-fold, and they decrease again during G(2) phase. Replication-dependent histone mRNAs are the only metazoan mRNAs that lack polyadenylated tails, ending instead in a conserved stem-loop. Much of the cell cycle regulation is posttranscriptional and is mediated by the 3' stem-loop. A 31-kDa stem-loop binding protein (SLBP) binds the 3' end of histone mRNA. The SLBP is necessary for pre-mRNA processing and accompanies the histone mRNA to the cytoplasm, where it is a component of the histone messenger RNP. We used synchronous CHO cells selected by mitotic shakeoff and HeLa cells synchronized at the G(1)/S or the M/G(1) boundary to study the regulation of SLBP during the cell cycle. In each system the amount of SLBP is regulated during the cell cycle, increasing 10- to 20-fold in the late G(1) and then decreasing in the S/G(2) border. SLBP mRNA levels are constant during the cell cycle. SLBP is regulated at the level of translation as cells progress from G(1) to S phase, and the protein is rapidly degraded as they progress into G(2). Regulation of SLBP may account for the posttranscriptional component of the cell cycle regulation of histone mRNA.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Whitfield
authors.forename: L X
authors.initials: LX
authors.lastname: Zheng
authors.forename: A
authors.initials: A
authors.lastname: Baldwin
authors.forename: T
authors.initials: T
authors.lastname: Ohta
authors.forename: M M
authors.initials: MM
authors.lastname: Hurt
authors.forename: W F
authors.initials: WF
authors.lastname: Marzluff
mesh_terms: D000818:Animals; D016466:CHO Cells; D002453:Cell Cycle; D006224:Cricetinae; D004261:DNA Replication; D006657:Histones / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D006657:Histones; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins