c-ETS transcription factors play an essential role in the licensing of human MCM4 origin of replication

• c-ETS transcription factors were identified as novel regulatory molecules that bound to the human MCM4 ori.
• c-ETS2 and c-ETS1 respectively bind to the ori during the G1 and S phases of cell cycle without impacting transcription.
• The ori undergoes a sequential acetylation of histones, c-ETS2 recruitment and loading of pre-RC components in the G1 phase.
• c-ETS2 recruitment promotes replication licensing at MCM4 ori whereas c-ETS1 seems to repress it.

In metazoans, DNA replication is a highly regulated and ordered process that occurs during the S phase of cell cycle. It begins with the licensing of origins of replication usually found in close proximity of actively transcribing genes owing perhaps to a profound influence of transcription factors on the epigenetic signatures and architecture of chromatin. Here we show that ETS transcription factors are novel regulators of MCM4 origin, whose binding sites are localized between two divergently transcribing MCM4 and PRKDC genes. c-ETS1 and c-ETS2 were recruited to the MCM4 origin respectively during the S and G1 phases of cell cycle. c-ETS2 binding was facilitated by an active chromatin distinguished by acetylated histone H3 orchestrated by histone acetyl transferase GCN5 and followed by HBO1 mediated histone H4 acetylation. Interestingly, c-ETS2 overexpression led to increased BrdU incorporation in the S phase cells while its down-regulation by RNA interference compromised the loading of pre-replicative complex at the origin. Conversely, the recruitment of c-ETS1 at the origin coincided with histone H3 methylation signature characteristic of closed chromatin conformation. As expected, enforced expression of c-ETS1 severely compromised DNA replication whereas its down-regulation enhanced DNA replication as evident from increased BrdU incorporation. Thus, c-ETS transcription factors appear to be key regulators of MCM4 origin where c-ETS2 seems to promote DNA replication whereas c-ETS1 functions as a negative regulator.

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