Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena

The intra-S phase checkpoint kinase of metazoa and yeast, ATR/MEC1, protects chromosomes from DNA damage and replication stress by phosphorylating subunits of the replicative helicase, MCM2-7. Here we describe an unprecedented ATR-dependent pathway in Tetrahymena thermophila in which the essential p...

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Main Authors:	Sandoval, Pamela Y., Lee, Po-Hsuen, Meng, Xiangzhou, Kapler, Geoffrey M.
Format:	Online
Language:	English
Published:	Public Library of Science 2015
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4517752/

id	pubmed-4517752
recordtype	oai_dc
spelling	pubmed-45177522015-07-31 Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena Sandoval, Pamela Y. Lee, Po-Hsuen Meng, Xiangzhou Kapler, Geoffrey M. Research Article The intra-S phase checkpoint kinase of metazoa and yeast, ATR/MEC1, protects chromosomes from DNA damage and replication stress by phosphorylating subunits of the replicative helicase, MCM2-7. Here we describe an unprecedented ATR-dependent pathway in Tetrahymena thermophila in which the essential pre-replicative complex proteins, Orc1p, Orc2p and Mcm6p are degraded in hydroxyurea-treated S phase cells. Chromosomes undergo global changes during HU-arrest, including phosphorylation of histone H2A.X, deacetylation of histone H3, and an apparent diminution in DNA content that can be blocked by the deacetylase inhibitor sodium butyrate. Most remarkably, the cell cycle rapidly resumes upon hydroxyurea removal, and the entire genome is replicated prior to replenishment of ORC and MCMs. While stalled replication forks are elongated under these conditions, DNA fiber imaging revealed that most replicating molecules are produced by new initiation events. Furthermore, the sole origin in the ribosomal DNA minichromosome is inactive and replication appears to initiate near the rRNA promoter. The collective data raise the possibility that replication initiation occurs by an ORC-independent mechanism during the recovery from HU-induced replication stress. Public Library of Science 2015-07-28 /pmc/articles/PMC4517752/ /pubmed/26218270 http://dx.doi.org/10.1371/journal.pgen.1005405 Text en © 2015 Sandoval et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Sandoval, Pamela Y. Lee, Po-Hsuen Meng, Xiangzhou Kapler, Geoffrey M.
spellingShingle	Sandoval, Pamela Y. Lee, Po-Hsuen Meng, Xiangzhou Kapler, Geoffrey M. Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena
author_facet	Sandoval, Pamela Y. Lee, Po-Hsuen Meng, Xiangzhou Kapler, Geoffrey M.
author_sort	Sandoval, Pamela Y.
title	Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena
title_short	Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena
title_full	Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena
title_fullStr	Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena
title_full_unstemmed	Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena
title_sort	checkpoint activation of an unconventional dna replication program in tetrahymena
description	The intra-S phase checkpoint kinase of metazoa and yeast, ATR/MEC1, protects chromosomes from DNA damage and replication stress by phosphorylating subunits of the replicative helicase, MCM2-7. Here we describe an unprecedented ATR-dependent pathway in Tetrahymena thermophila in which the essential pre-replicative complex proteins, Orc1p, Orc2p and Mcm6p are degraded in hydroxyurea-treated S phase cells. Chromosomes undergo global changes during HU-arrest, including phosphorylation of histone H2A.X, deacetylation of histone H3, and an apparent diminution in DNA content that can be blocked by the deacetylase inhibitor sodium butyrate. Most remarkably, the cell cycle rapidly resumes upon hydroxyurea removal, and the entire genome is replicated prior to replenishment of ORC and MCMs. While stalled replication forks are elongated under these conditions, DNA fiber imaging revealed that most replicating molecules are produced by new initiation events. Furthermore, the sole origin in the ribosomal DNA minichromosome is inactive and replication appears to initiate near the rRNA promoter. The collective data raise the possibility that replication initiation occurs by an ORC-independent mechanism during the recovery from HU-induced replication stress.
publisher	Public Library of Science
publishDate	2015
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4517752/
_version_	1613253138638176256

Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena

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