Activation-induced cytidine deaminase (AID)-dependent somatic hypermutation requires a splice isoform of the serine/arginine-rich (SR) protein SRSF1

Yuichi Kanehiro, Kagefumi Todo, Misaki Negishi, Junji Fukuoka, Wenjian Gan, Takuya Hikasa, Yoshiaki Kaga, Masayuki Takemoto, Masaki Magari, Xialu Li, James L. Manley, Hitoshi Ohmori, Naoki Kanayama

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Somatic hypermutation (SHM) of Ig variable region (IgV) genes requires both IgV transcription and the enzyme activation-induced cytidine deaminase (AID). Identification of a cofactor responsible for the fact that IgV genes are much more sensitive to AID-induced mutagenesis than other genes is a key question in immunology. Here, we describe an essential role for a splice isoform of the prototypical serine/arginine-rich (SR) protein SRSF1, termed SRSF1-3, in AID-induced SHM in a DT40 chicken B-cell line. Unexpectedly, we found that SHM does not occur in a DT40 line lacking SRSF1-3 (DT40-ASF), although it is readily detectable in parental DT40 cells. Strikingly, overexpression of AID in DT40-ASF cells led to a large increase in nonspecific (off-target) mutations. In contrast, introduction of SRSF1-3, but not SRSF1, into these cells specifically restored SHM without increasing off-target mutations. Furthermore, we found that SRSF1-3 binds preferentially to the IgV gene and inhibits processing of the Ig transcript, providing a mechanism by which SRSF1-3 makes the IgV gene available for AID-dependent SHM. SRSF1 not only acts as an essential splicing factor but also regulates diverse aspects of mRNA metabolism and maintains genome stability. Our findings, thus, define an unexpected and important role for SRSF1, particularly for its splice variant, in enabling AID to function specifically on its natural substrate during SHM.

Original languageEnglish
Pages (from-to)1216-1221
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number4
DOIs
Publication statusPublished - Jan 24 2012

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Immunoglobulin Variable Region
Serine
Arginine
Protein Isoforms
Proteins
Transcriptional Activation
Genes
Mutation
Enzyme Activation
Genomic Instability
Allergy and Immunology
Mutagenesis
AICDA (activation-induced cytidine deaminase)
Chickens
B-Lymphocytes
Cell Line
Messenger RNA

Keywords

  • Gene conversion
  • Genomic instability

ASJC Scopus subject areas

  • General

Cite this

Activation-induced cytidine deaminase (AID)-dependent somatic hypermutation requires a splice isoform of the serine/arginine-rich (SR) protein SRSF1. / Kanehiro, Yuichi; Todo, Kagefumi; Negishi, Misaki; Fukuoka, Junji; Gan, Wenjian; Hikasa, Takuya; Kaga, Yoshiaki; Takemoto, Masayuki; Magari, Masaki; Li, Xialu; Manley, James L.; Ohmori, Hitoshi; Kanayama, Naoki.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 109, No. 4, 24.01.2012, p. 1216-1221.

Research output: Contribution to journalArticle

Kanehiro, Yuichi ; Todo, Kagefumi ; Negishi, Misaki ; Fukuoka, Junji ; Gan, Wenjian ; Hikasa, Takuya ; Kaga, Yoshiaki ; Takemoto, Masayuki ; Magari, Masaki ; Li, Xialu ; Manley, James L. ; Ohmori, Hitoshi ; Kanayama, Naoki. / Activation-induced cytidine deaminase (AID)-dependent somatic hypermutation requires a splice isoform of the serine/arginine-rich (SR) protein SRSF1. In: Proceedings of the National Academy of Sciences of the United States of America. 2012 ; Vol. 109, No. 4. pp. 1216-1221.
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AU - Kanehiro, Yuichi

AU - Todo, Kagefumi

AU - Negishi, Misaki

AU - Fukuoka, Junji

AU - Gan, Wenjian

AU - Hikasa, Takuya

AU - Kaga, Yoshiaki

AU - Takemoto, Masayuki

AU - Magari, Masaki

AU - Li, Xialu

AU - Manley, James L.

AU - Ohmori, Hitoshi

AU - Kanayama, Naoki

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N2 - Somatic hypermutation (SHM) of Ig variable region (IgV) genes requires both IgV transcription and the enzyme activation-induced cytidine deaminase (AID). Identification of a cofactor responsible for the fact that IgV genes are much more sensitive to AID-induced mutagenesis than other genes is a key question in immunology. Here, we describe an essential role for a splice isoform of the prototypical serine/arginine-rich (SR) protein SRSF1, termed SRSF1-3, in AID-induced SHM in a DT40 chicken B-cell line. Unexpectedly, we found that SHM does not occur in a DT40 line lacking SRSF1-3 (DT40-ASF), although it is readily detectable in parental DT40 cells. Strikingly, overexpression of AID in DT40-ASF cells led to a large increase in nonspecific (off-target) mutations. In contrast, introduction of SRSF1-3, but not SRSF1, into these cells specifically restored SHM without increasing off-target mutations. Furthermore, we found that SRSF1-3 binds preferentially to the IgV gene and inhibits processing of the Ig transcript, providing a mechanism by which SRSF1-3 makes the IgV gene available for AID-dependent SHM. SRSF1 not only acts as an essential splicing factor but also regulates diverse aspects of mRNA metabolism and maintains genome stability. Our findings, thus, define an unexpected and important role for SRSF1, particularly for its splice variant, in enabling AID to function specifically on its natural substrate during SHM.

AB - Somatic hypermutation (SHM) of Ig variable region (IgV) genes requires both IgV transcription and the enzyme activation-induced cytidine deaminase (AID). Identification of a cofactor responsible for the fact that IgV genes are much more sensitive to AID-induced mutagenesis than other genes is a key question in immunology. Here, we describe an essential role for a splice isoform of the prototypical serine/arginine-rich (SR) protein SRSF1, termed SRSF1-3, in AID-induced SHM in a DT40 chicken B-cell line. Unexpectedly, we found that SHM does not occur in a DT40 line lacking SRSF1-3 (DT40-ASF), although it is readily detectable in parental DT40 cells. Strikingly, overexpression of AID in DT40-ASF cells led to a large increase in nonspecific (off-target) mutations. In contrast, introduction of SRSF1-3, but not SRSF1, into these cells specifically restored SHM without increasing off-target mutations. Furthermore, we found that SRSF1-3 binds preferentially to the IgV gene and inhibits processing of the Ig transcript, providing a mechanism by which SRSF1-3 makes the IgV gene available for AID-dependent SHM. SRSF1 not only acts as an essential splicing factor but also regulates diverse aspects of mRNA metabolism and maintains genome stability. Our findings, thus, define an unexpected and important role for SRSF1, particularly for its splice variant, in enabling AID to function specifically on its natural substrate during SHM.

KW - Gene conversion

KW - Genomic instability

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