Altered CELF1 binding to target transcripts in malignant T cells

RNA. 2015 Oct;21(10):1757-69. doi: 10.1261/rna.049940.115. Epub 2015 Aug 6.

Abstract

The RNA-binding protein, CELF1, binds to a regulatory sequence known as the GU-rich element (GRE) and controls a network of mRNA transcripts that regulate cellular activation, proliferation, and apoptosis. We performed immunoprecipitation using an anti-CELF1 antibody, followed by identification of copurified transcripts using microarrays. We found that CELF1 is bound to a distinct set of target transcripts in the H9 and Jurkat malignant T-cell lines, compared with primary human T cells. CELF1 was not phosphorylated in resting normal T cells, but in malignant T cells, phosphorylation of CELF1 correlated with its inability to bind to GRE-containing mRNAs that served as CELF1 targets in normal T cells. Lack of binding by CELF1 to these mRNAs in malignant T cells correlated with stabilization and increased expression of these transcripts. Several of these GRE-containing transcripts that encode regulators of cell growth were also stabilized and up-regulated in primary tumor cells from patients with T-cell acute lymphoblastic leukemia. Interestingly, transcripts encoding numerous suppressors of cell proliferation that served as targets of CELF1 in malignant T cells, but not normal T cells, exhibited accelerated degradation and reduced expression in malignant compared with normal T cells, consistent with the known function of CELF1 to mediate degradation of bound transcripts. Overall, CELF1 dysfunction in malignant T cells led to the up-regulation of a subset of GRE-containing transcripts that promote cell growth and down-regulation of another subset that suppress cell growth, producing a net effect that would drive a malignant phenotype.

Keywords: CELF1 phosphorylation; GRE; GU-rich element; cancer; mRNA stability.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • CELF1 Protein / metabolism*
  • Humans
  • Phosphorylation
  • Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / metabolism*
  • Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / pathology
  • Protein Binding
  • RNA, Messenger / metabolism*
  • T-Lymphocytes / metabolism*

Substances

  • CELF1 Protein
  • CELF1 protein, human
  • RNA, Messenger