A CPF-like phosphatase module links transcription termination to chromatin silencing
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Abstract
The interconnections between co-transcriptional regulation, chromatin environment and transcriptional output remain poorly understood. Here, we investigate the mechanism underlying RNA 3 processing-mediated Polycomb silencing of Arabidopsis FLOWERING LOCUS C (FLC). We show a requirement for APRF1, a homologue of yeast Swd2 and human WDR82, known to regulate RNA Pol II during transcription termination. APRF1 interacts with TOPP4 (yeast Glc7/human PP1) and LD, the latter showing structural features found in Ref2/PNUTS; all components of the yeast and human phosphatase module of the CPF 3 end processing machinery. LD has been shown to co-associate in vivo with the histone H3 K4 demethylase FLD. We show APRF1 and LD couple CPF-mediated cleavage and polyadenylation with removal of H3K4 monomethylation in the body of FLC, and this influences subsequent transcription. This work shows how transcription termination can change the local chromatin environment to modulate transcription of Arabidopsis FLC and affect flowering time.
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The work here identifies the importance of the CPSF phosphatase module, a regulator of RNA Pol II,307in FLC regulation
This is a beautiful study describing the regulation of the FLC locus. Do you believe APRF1, TOPP4, and LD are specific regulators of only FLC? Or do they play a more general role in regulating repression/activation at many loci? If so, do you have any genome-wide information on how APRF1, TOPP4, and LD mutants effect other genes, particularly those involved in sensing environment cues, like you've examined with flowering? And, if their role is not restricted to regulating FLC, what other phenotypes do you observe with these mutants--do the phenotypes give you insights into other processes they may regulate?
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Taken together, the robust202immunoprecipitation of LD and TOPP4 by APRF1, the structural parallels between Ref2-PNUTS-LD203and the similar roles in co-transcriptional processing lead us to propose that LD, APRF1, and TOPP4204may form a functional CPSF phosphatase module in plants
It will be exciting to see if these putative subunits possess phosphatase activity, in vitro, and further dissect how this phosphatase activity might be regulated.
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Thus, APRF1 has a role in establishing a silent152chromatin status at FLC (Figure 1H, I)
The evidence that APRF1 is regulating flc expression is strong; however, given APRF1's likely role in regulating a wide range of genes, do you have evidence that APRF1 is directly associating with the flc locus to regulate expression and that the regulation is not indirect?
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