Ustilago maydisTrf2 ensures genome stability by antagonizing Blm-mediated telomere recombination: fine-tuning DNA repair factor activity at telomeres through opposing regulations

Author:

Syed Shahrez,Aloe Sarah,Sutherland Jeanette H.,Holloman William K.ORCID,Lue Neal F.ORCID

Abstract

AbstractTRF2 is an essential and conserved double-strand telomere binding protein that stabilizes chromosome ends by suppressing DNA damage response and aberrant DNA repair. Herein we investigated the mechanisms and functions of the Trf2 ortholog in the basidiomycete fungusUstilago maydis,which manifests strong resemblances to metazoans with regards to the telomere and DNA repair machinery. We showed thatUmTrf2 binds to Blmin vitroand inhibits Blm-mediated unwinding of telomeric DNA substrates. Consistent with a similar inhibitory activityin vivo, over-expression of Trf2 induces telomere shortening, just like deletion ofblm,which is required for efficient telomere replication. While the loss of Trf2 engenders growth arrest and multiple telomere aberrations, these defects are fully suppressed by the concurrent deletion ofblmormre11(but not other DNA repair factors). Over-expression of Blm alone triggers aberrant telomere recombination and the accumulation of aberrant telomere structures, which are blocked by concurrent Trf2 over-expression. Together, these findings highlight the suppression of Blm as a key protective mechanism of Trf2. Notably,U. maydisharbors another double-strand telomere-binding protein (Tay1), which promotes Blm activity to ensure efficient replication. We found that deletion oftay1partially suppresses the telomere aberration of Trf2-depleted cells. Our results thus point to opposing regulation of Blm helicase by telomere proteins as a strategy for optimizing both telomere maintenance and protection. We also show that aberrant transcription of both telomere G- and C-strand is a recurrent phenotype of telomere mutants, underscoring another potential similarity between double strand breaks and de-protected telomeres.Author SummaryThe ends of linear chromosomes are protected from abnormal repair by a collection of telomere proteins. One protein that plays an especially prominent role is TRF2, which binds to double-stranded telomere repeats. In this study, we analyzed the mechanisms and functions of Trf2 in a yeast-like fungus namedUstilago maydis, which manifests a high degree of similarity to animal cells with respect to telomere regulation. We showed that Trf2 binds directly to a conserved DNA helicase called Blm and inhibits the ability of Blm to unwind telomeric DNA in a purified, cell-free reaction. We also used over-expression and depletion of either Trf2 or Blm or both to demonstrate an inhibitory effect of Trf2 on Blm functionin vivo. For example, depletion of Trf2 triggers Blm-dependent telomere aberrations and cell death. Interestingly, another double-strand telomere binding protein named Tay1 was found to stimulate Blm activity to promote telomere replication. Together, our results indicate thatU. maydisoptimizes Blm function through opposing regulation of its activity via distinct telomere proteins. We also detected high levels of abnormal transcripts that correspond to both strands of telomeres in a variety of telomere mutants, suggesting that de-protected telomeres are permissive substrates for the transcription apparatus.

Publisher

Cold Spring Harbor Laboratory

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3