Altered CELF1 binding to target transcripts in malignant T cells
- Paul R. Bohjanen1,2,3,
- Mai Lee Moua1,3,
- Liang Guo1,3,
- Ammanuel Taye1,3 and
- Irina A. Vlasova-St. Louis1,3
- 1Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA
- 2Department of Microbiology, University of Minnesota, Minneapolis, Minnesota 55455, USA
- 3Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota, Minneapolis, Minnesota 55455, USA
- Corresponding author: vlaso001{at}umn.edu
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.
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Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.049940.115.
- Received January 19, 2015.
- Accepted June 29, 2015.
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