C-terminal domain (CTD) phosphatase links Rho GTPase signaling to Pol II CTD phosphorylation in Arabidopsis and yeast

Abstract

Rho GTPases, including the Rho, Cdc42, Rac, and ROP subfamilies, act as pivotal signaling switches in various growth and developmental processes. Compared with the well-defined role of cytoskeletal organization in Rho signaling, much less is known regarding transcriptional regulation. In a mutant screen for phenotypic enhancers of transgenic Arabidopsis plants expressing a constitutively active form of ROP2 (designated CA1-1), we identified RNA polymerase II (Pol II) C-terminal domain (CTD) phosphatase-like 1 (CPL1) as a transcriptional regulator of ROP2 signaling. We show that ROP2 activation inhibits CPL1 activity by promoting its degradation, leading to an increase in CTD Ser5 and Ser2 phosphorylation. We also observed similar modulation of CTD phosphorylation by yeast Cdc42 GTPase and enhanced degradation of the yeast CTD phosphatase Fcp1 by activated ROP2 signaling. Taken together, our results suggest that modulation of the Pol II CTD code by Rho GTPase signaling represents an evolutionarily conserved mechanism in both unicellular and multicellular eukaryotes.Rho GTPase | ROP GTPase | Pol II | CTD code | CPL1

Ras and Rho GTPase regulation of Pol II transcription: A shortcut model revisited

“…As yeast Ras-PKA signaling was not shown to modulate the CTD Ser phosphorylation code, 16 a test was performed to determine whether yeast uses Rho rather than Ras family GTPases to modulate the CTD code. 27 Genetic analysis suggests that a Cdc42 loss-of-function mutation in fission yeast led to much lower Ser2P and Ser5P. Together with the observation that the induction of Arabidopsis CA-rop2 also caused cell shape and Ser2P and Ser5P changes, these results show that Rho GTPase signaling modulation of the CTD code is evolutionarily conserved in unicellular (yeast) and multicellular (Arabidopsis) eukaryotes.…”

“…A very recent study has demonstrated that Rho GTPase signaling can directly target the Pol II CTD code and effect large-scale gene expression. 27 This link from Rho signaling to Pol II transcription was first revealed in an Arabidopsis cell morphogenic study. Constitutive activation of ROP2 (designated CA-rop2; a G12V mutation) leads to the conversion of interdigitated cotyledon pavement cells to the fat, hyper-parallel, near-rectangular shape, but a recessive mutation in the CTD phosphatase gene CPL1 further enhances the shape phenotype along with the enhancement in cell size and cell number phenotypes.…”

“…Constitutive activation of ROP2 (designated CA-rop2; a G12V mutation) leads to the conversion of interdigitated cotyledon pavement cells to the fat, hyper-parallel, near-rectangular shape, but a recessive mutation in the CTD phosphatase gene CPL1 further enhances the shape phenotype along with the enhancement in cell size and cell number phenotypes. 27 CA-rop2 overexpression causes an increase in the CTD Ser2P and Ser5P levels but not Ser7P, indicating that Ser2-and Ser5-specific phosphorylation pattern is impacted. This modulation is mediated by promoting CPL1 degradation.…”

“…Clearly, these recent findings in both yeasts and Arabidopsis plants suggest that modulation of the Pol II CTD code by Rho GTPase signaling via the degradation of CTD phosphatases represents an evolutionarily conserved mechanism in intracellular signaling. 27 This shortcut model (Fig. 1) allows cells to quickly respond to extracellular signals (such as the plant hormone auxin), leading to the activation of Rho GTPases.…”

Dynamic regulation of HYL1 provides new insights into its multifaceted role in Arabidopsis

“…The dynamic phosphorylation of two serine residues S 2 and S 5 has been observed in CTD repeats by MAP kinases ERK1/2 in human, yeast and Xenopus laevis Oocyte. In plants, MPK3 phosphorylates RNA pol II and regulates its activity (Bellier et al, 1997; Bonnet et al, 1999; Prelich et al, 2009; Glover-cutter et al, 2009; Zhang et al, 2016). The dephosphorylation of CTD by CPL1 is associated with transcription initiation by interaction of RNA pol II at the promoter with TATA binding proteins.…”