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

Abstract

Proper cell cycle-dependent expression of replicationdependent histones is essential for packaging of DNA into chromatin during replication. We previously showed that cyclin-dependent kinase-9 (CDK9) controls histone H2B monoubiquitination (H2Bub1) to direct the recruitment of specific mRNA 3 0 end processing proteins to replicationdependent histone genes and promote proper pre-mRNA 3 0 end processing. We now show that p53 decreases the expression of the histone-specific transcriptional regulator Nuclear Protein, Ataxia-Telangiectasia Locus (NPAT) by inducing a G1 cell-cycle arrest, thereby affecting E2F-dependent transcription of the NPAT gene. Furthermore, NPAT is essential for histone mRNA 3 0 end processing and recruits CDK9 to replication-dependent histone genes. Reduced NPAT expression following p53 activation or small interfering RNA knockdown decreases CDK9 recruitment and replication-dependent histone gene transcription but increases the polyadenylation of remaining histone mRNAs. Thus, we present evidence that the induction of a G1 cell-cycle arrest (for example, following p53 accumulation) alters histone mRNA 3 0 end processing and uncover the first mechanism of a regulated switch in the mode of pre-mRNA 3 0 end processing during a normal cellular process, which may be altered during tumorigenesis.

CstF64: Cell Cycle Regulation and Functional Role in 3′ End Processing of Replication-Dependent Histone mRNAs

“…A similar accumulation of read-through transcripts has previously been described after the depletion of several other factors important for histone RNA processing (22)(23)(24)(25). In agreement with these previous studies, we could show that the majority of free RNA is present in earlier fractions and ribosomes and polysomes in later fractions.…”

“…2E), we wanted to characterize their nature, metabolism, and potential function. Several reports suggested that upon misprocessing, replicationdependent histone transcripts acquire a poly(A) tail (22)(23)(24)(25). Indeed, we found by in silico analysis that several members of the human replication-dependent histone genes contain cryptic polyadenylation signals downstream of the canonical cleavage sites.…”

“…6). As many human histone genes contain cryptic polyadenylation sites downstream of the canonical cleavage site, this might represent a safety mechanism to avoid read-through into neighboring genes in the tightly packed histone gene clusters, as previously suggested (22)(23)(24)(25). In case of misprocessing during pervasive transcription in the S phase, read-through might otherwise result in fusion transcripts that could be deleterious, especially if they would be exported to the cytoplasm and translated.…”

“…Additionally, it was shown that if normal processing is prevented, histone transcripts can become polyadenylated at downstream poly(A) sites (22)(23)(24)(25). However, neither a possible function nor the metabolism of these transcripts has been characterized.…”

Germacrone inhibits the proliferation of glioma cells by promoting apoptosis and inducing cell cycle arrest

“…It negatively regulates the G1/S phase transition and its up-regulation results in cell cycle arrest in G1 phase (20). In association with CDK2 complexes, it inhibits kinase activity and blocks cell cycle progression through G1/S arrest (21).…”