CFIm25 regulates glutaminase alternative terminal exon definition to modulate miR-23 function.
Alternative polyadenylation (APA) and alternative splicing (AS) provide mRNAs with the means to avoid microRNA repression through selective shortening or differential usage of 3'UTRs. The two glutaminase (GLS) mRNA isoforms, termed KGA and GAC, contain distinct 3'UTRs with the KGA isoform subject to repression by miR-23. We show that depletion of the APA regulator CFIm25 causes a strong shift to the usage of a proximal poly(A) site within the KGA 3'UTR and also alters splicing to favor exclusion of the GAC 3'UTR. Surprisingly, we observe that while miR-23 is capable of down-regulating the shortened KGA 3'UTR, it has only minor impact on the full-length KGA 3'UTR, demonstrating that additional potent negative regulation of GLS expression exists beyond this single microRNA targeting site. Finally, we show that the apoptosis induced upon down-regulation of the GAC isoform can be alleviated through concurrent reduction in CFIm25 expression, revealing the sensitivity of glutaminase expression to the levels of RNA processing factors. These results exemplify the complex interplay between RNA processing and microRNA repression in controlling glutamine metabolism in cancer cells.
Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas 77030, USA.
Chioniso P
CP
Masamha
Division of Biostatistics, Dan L. Duncan Cancer Center and Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Zheng
Z
Xia
Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas 77030, USA The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
Natoya
N
Peart
Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas 77030, USA The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
Scott
S
Collum
Division of Biostatistics, Dan L. Duncan Cancer Center and Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Wei
W
Li
Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas 77030, USA The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
Eric J
EJ
Wagner
Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas 77030, USA The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
Ann-Bin
AB
Shyu
D020413:3' Untranslated Regions; D017398:Alternative Splicing; D005091:Exons; D005972:Glutaminase / Q000235:genetics*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000235:genetics; D035683:MicroRNAs / Q000502:physiology*; D011061:Poly A / Q000378:metabolism; D026723:Polyadenylation
D020413:3' Untranslated Regions; D007527:Isoenzymes; C552430:MIRN23a microRNA, human; D035683:MicroRNAs; D011061:Poly A; D005972:Glutaminase
alternative polyadenylation; c-Myc; cell growth; glutaminase; glutamine addiction; miRNA