NPAT links cyclin E–Cdk2 to the regulation of replication-dependent histone gene transcription

Abstract

In eukaryotic cells, histone gene expression is one of the major events that mark entry into S phase. While this process is tightly linked to cell cycle position, how it is regulated by the cell cycle machinery is not known. Here we show that NPAT, a substrate of the cyclin E-Cdk2 complex, is associated with human replication-dependent histone gene clusters on both chromosomes 1 and 6 in S phase. We demonstrate that NPAT activates histone gene transcription and that this activation is dependent on the promoter elements (SSCSs) previously proposed to mediate cell cycle-dependent transcription. Cyclin E is also associated with the histone gene loci, and cyclin E-Cdk2 stimulates the NPAT-mediated activation of histone gene transcription. Thus, our results both show that NPAT is involved in a key S phase event and provide a link between the cell cycle machinery and activation of histone gene transcription.

Cell cycle dependent phosphorylation and subnuclear organization of the histone gene regulator p220NPAT in human embryonic stem cells

“…The interpretation of in situ microscopy data of Cajal bodies and related structures is further complicated by the technical limitation that no more than three or four components can be visualized at any one time. In addition, the histone gene cluster at Chromosome 6 is constitutively associated with Cajal bodies, whereas the histone gene cluster at Chromosome 1 is only associated with Cajal bodies when somatic cells progress into S phase Zhao et al, 2000). The number of p220 NPAT foci typically doubles from two to four as somatic cells progress into S phase, and this duplication correlates with the cell cycle dependent association of the Chromosome 1 histone gene cluster.…”

“…One principal event during the somatic cell cycle is the induction of the HiNF-P/ p220 NPAT co-activation complex by CDK dependent phosphorylation of p220 NPAT (Zhao et al, 1998(Zhao et al, , 2000Ma et al, 2000;Mitra et al, 2003;Wei et al, 2003;Ye et al, 2003;Miele et al, 2005). Here we examine the appearance of subnuclear foci containing p220 NPAT and phosphorylation of p220 NPAT in ES cells to understand the regulation of the G1/S phase transition relative to somatic cells.…”

“…Similar to somatic cells, ES cells express histone gene regulatory factors (e.g., HiNF-P and p220 NPAT ) and exhibit S phase specific expression of distinct members of the DNA replication dependent histone gene family (Becker et al, 2006(Becker et al, , 2007. In somatic cells, critical events for the onset of S phase include the cell cycle dependent phosphorylation of p220 NPAT by cyclin E/CDK2 at nuclear foci related to Cajal bodies and the subsequent recruitment of p220 NPAT by transcription factor HiNF-P to histone H4 gene promoters (Zhao et al, 1998(Zhao et al, , 2000Ma et al, 2000;Mitra et al, 2003;Wei et al, 2003;Ye et al, 2003;Miele et al, 2005).…”

Induced G1 cell-cycle arrest controls replication-dependent histone mRNA 3′ end processing through p21, NPAT and CDK9

“…Nuclear Protein, Ataxia-Telangiectasia Locus (NPAT/ p220) stimulates the transcription of all replicationdependent histone genes during S phase (Gao et al, 2003;Ye et al, 2003) in a phosphorylation-dependent manner (Zhao et al, 1998(Zhao et al, , 2000Ma et al, 2000). NPAT functions, in part, by recruiting coactivator proteins including histone-modifying enzymes (DeRan et al, 2008).…”

DNA-PK phosphorylation sites on Oct-1 promote cell survival following DNA damage

“…Oct-1 binding to the H2B promoter is unaffected by DNA damage Oct-1 is readily visualized on the H2B promoter in proliferating cells (Zhao et al, 2000b). In response to IR treatment, H2B transcription decreases (MeighanMantha et al, 1999;Schild-Poulter et al, 2003;Su et al, 2004), suggesting that phosphorylation of Oct-1 in response to IR could influence the recruitment of Oct-1 to the histone H2B promoter.…”