The MAF1 Phosphoregulatory Region Controls MAF1 Interaction with the RNA Polymerase III C34 Subunit and Transcriptional Repression in Plants

Author(s)

Andrade, Maxuel Oliveira ^[1] ; Sforca, Mauricio Luis ^[1] ; Heleno Batista, Fernanda Aparecida ^[1] ; Migliorini Figueira, Ana Carolina ^[1] ; Benedetti, Celso Eduardo ^[1]

Affiliation

^[1] Brazilian Ctr Res Energy & Mat, Brazilian Biosci Natl Lab, BR-13083100 Campinas, SP - Brazil

• Document type: Journal article
• Source: PLANT CELL; v. 32, n. 9, p. 3019-3035, SEP 2020.
• Web of Science Citations: 1

Abstract

The phosphoregulatory region of citrus MAF1 not only contributes to, but also regulates the binding of MAF1 to the C34 subunit of RNA polymerase III. MAF1 is a phosphoprotein that plays a critical role in cell growth control as the central regulator of RNA polymerase (Pol) III activity. Citrus MAF1 (CsMAF1) was identified as a direct target of PthA4, a bacterial effector protein required to induce tumors in citrus. CsMAF1 binds to Pol III to restrict transcription; however, exactly how CsMAF1 interacts with the polymerase and how phosphorylation modulates this interaction is unknown. Moreover, how CsMAF1 binds PthA4 is also obscure. Here we show that CsMAF1 binds predominantly to the WH1 domain of the citrus Pol III subunit C34 (CsC34) and that its phosphoregulatory region, comprising loop-3 and alpha-helix-2, contributes to this interaction. We also show that phosphorylation of this region decreases CsMAF1 affinity to CsC34, leading to Pol III derepression, and that Ser 45, found only in plant MAF1 proteins, is critical for CsC34 interaction and is phosphorylated by a new citrus AGC1 kinase. Additionally, we show that the C-terminal region of the citrus TFIIIB component BRF1 competes with CsMAF1 for CsC34 interaction, whereas the C-terminal region of CsMAF1 is essential for PthA4 binding. Based on CsMAF1 structural data, we propose a mechanism for how CsMAF1 represses Pol III transcription and how phosphorylation controls this process. (AU)

• FAPESP's process: 17/18570-9 - Functional analysis of CsMAF1, an RNA polymerase III repressor involved in cell growth control and pathogen response in plants
• Grantee: Maxuel de Oliveira Andrade
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/08535-4 - Structural and functional analysis of the RNA polymerase III repressor Maf1 involved in cell growth control and pathogen response in plants
• Grantee: Celso Eduardo Benedetti
• Support Opportunities: Regular Research Grants
• FAPESP's process: 14/50880-0 - INCT 2014: comparative and functional genomics and citrus-assisted breeding
• Grantee: Marcos Antonio Machado
• Support Opportunities: Research Projects - Thematic Grants