PT  - JOURNAL ARTICLE
AU  - Jered M. Wendte
AU  - Jeremy R. Haag
AU  - Jasleen Singh
AU  - Anastasia McKinlay
AU  - Olga M. Pontes
AU  - Craig S. Pikaard
TI  - Subdomains of the Pol V largest subunit CTD mediate locus-specific RNA-directed DNA methylation
AID  - 10.1101/111831
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 111831
4099  - http://biorxiv.org/content/early/2017/02/25/111831.short
4100  - http://biorxiv.org/content/early/2017/02/25/111831.full
AB  - RNA Polymerase V transcription recruits siRNA-Argonaute protein complexes to chromatin, thereby specifying sites of RNA-directed DNA methylation (RdDM) and transcriptional gene silencing in plants. Pol V's largest subunit, NRPE1, has an extensive carboxyl-terminal domain (CTD) that is dispensable for catalytic activity in vitro, yet essential in vivo. A CTD subdomain, DeCL, named for its similarity to a chloroplast protein, DEFECTIVE CHLOROPLASTS AND LEAVES, is required for Pol V function at virtually all loci, similar to mutants defective for Pol V recruitment. Deletions removing three other CTD subdomains affect overlapping subsets of loci, similar to mutants lacking proteins that bind Pol V or its transcripts. A yeast two-hybrid screen for CTD-interactors identified the 3'->5' exoribonuclease, RRP6L1 as an interactor with the DeCL subdomain and the adjacent QS subdomain, named for its numerous glutamine-serine (QS) repeats. These RRP6L1-binding subdomains immediately follow the Argonaute-binding subdomain. Experimental evidence indicates that RRP6L1 trims the 3’ ends of Pol V transcripts sliced by ARGONAUTE 4 (AGO4), suggesting a model whereby the adjacent CTD subdomains enable the spatial and temporal coordination of AGO4 and RRP6L1 RNA processing activities.