Competitive regulation of alternative splicing and alternative polyadenylation by hnRNP H and CstF64 determines acetylcholinesterase isoforms.

Acetylcholinesterase (AChE), encoded by the ACHE gene, hydrolyzes the neurotransmitter acetylcholine to terminate synaptic transmission. Alternative splicing close to the 3΄ end generates three distinct isoforms of AChET, AChEH and AChER. We found that hnRNP H binds to two specific G-runs in exon 5a of human ACHE and activates the distal alternative 3΄ splice site (ss) between exons 5a and 5b to generate AChET. Specific effect of hnRNP H was corroborated by siRNA-mediated knockdown and artificial tethering of hnRNP H. Furthermore, hnRNP H competes for binding of CstF64 to the overlapping binding sites in exon 5a, and suppresses the selection of a cryptic polyadenylation site (PAS), which additionally ensures transcription of the distal 3΄ ss required for the generation of AChET. Expression levels of hnRNP H were positively correlated with the proportions of the AChET isoform in three different cell lines. HnRNP H thus critically generates AChET by enhancing the distal 3΄ ss and by suppressing the cryptic PAS. Global analysis of CLIP-seq and RNA-seq also revealed that hnRNP H competitively regulates alternative 3΄ ss and alternative PAS in other genes. We propose that hnRNP H is an essential factor that competitively regulates alternative splicing and alternative polyadenylation.

Citation

Mohammad Nazim, Akio Masuda, Mohammad Alinoor Rahman, Farhana Nasrin, Jun-Ichi Takeda, Kenji Ohe, Bisei Ohkawara, Mikako Ito, Kinji Ohno. Competitive regulation of alternative splicing and alternative polyadenylation by hnRNP H and CstF64 determines acetylcholinesterase isoforms. Nucleic acids research. 2017 Feb 17;45(3):1455-1468

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PMID: 28180311

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