Yeast Lacking the PP2A Phosphatase Regulatory Subunit Rts1 Sensitizes rad51 Mutants to Specific DNA Damaging Agents.

Mustapha Aouida,Dindial Ramotar,Abdelmoez Eshrif

doi:10.3389/fgene.2019.01117

Abstract

Rts1 is a regulatory subunit of the trimeric protein phosphatase 2A phosphatase and it participates in many biological processes by modulating the phosphorylation status of proteins. Consistent with its role, mutants lacking Rts1 display multiple phenotypes. We have previously performed a high throughput screen to search for yeast haploid mutants with altered sensitivity to the anticancer drug bleomycin, which acts by damaging the DNA to produce single and double strand breaks. RTS1 was among the genes that when singly deleted cause sensitivity to bleomycin. We investigate whether Rts1 plays a role in the repair of bleomycin-induced DNA lesions. We show that deletion of the RTS1 gene in the rad51 null background, lacking Rad51 known to be involved in the repair of bleomycin-induced DNA lesions, resulted in double mutants that were sensitized to bleomycin and not to other DNA damaging agents that creates DNA adducts. We further show that Rts1 has the ability to bind to DNA and in its absence cells displayed an increase in the frequency of both spontaneous and bleomycin-induced mutations compared to the parent. This is the first report implicating Rts1 with a role in DNA damage and repair, perhaps regulating the phosphorylation status of one or more proteins involved in the repair of DNA strand breaks.

Highlights

The protein phosphatase 2A (PP2A) is a heterotrimeric complex consisting of a catalytic subunit either Pph21, Pph22, or Pph3, the scaffolding subunit Tpd3, and a regulatory subunit Cdc55 or Rts1
We have previously identified from a high throughput screen of the yeast haploid mutant collection the RTS1 gene that when deleted cause the resulting rts1 mutant to be sensitive to the anticancer drug bleomycin (Aouida et al, 2004)
Since we have previously identified from a large scale screen that the RTS1 gene when deleted caused sensitivity to the DNA strand-breaking agent bleomycin (Aouida et al, 2004), we decided to examine more closely whether rts1Δ mutant would have a defect in DNA repair

Summary

Introduction

The protein phosphatase 2A (PP2A) is a heterotrimeric complex consisting of a catalytic subunit either Pph, Pph, or Pph, the scaffolding subunit Tpd, and a regulatory subunit Cdc or Rts. The overexpression of Rts can rescue some of the phenotypes such as genotoxic stress displayed by the absence of the histone acetyltransferase Gcn. The overexpression of Rts can rescue some of the phenotypes such as genotoxic stress displayed by the absence of the histone acetyltransferase Gcn5 This rescue effect may be related to the coordinated regulation between phosphorylation and acetylation, whereby the phosphorylation of serine 10 promotes acetylation of lysine 14 on histone H3 (Lo et al, 2000). In the absence of Rts, the SPS-pathway constitutively expressed Agp and Bap, indicating that Rts can exert control on gene expression (Zhao et al, 1997; Janssens and Goris, 2001; EckertBoulet et al, 2006). Rts can influence the functioning of several physiological pathways

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