Complex alternative splicing of human Endonuclease V mRNA, but evidence for only a single protein isoform

PLoS One. 2019 Nov 8;14(11):e0225081. doi: 10.1371/journal.pone.0225081. eCollection 2019.

Abstract

Endonuclease V (ENDOV) is a ribonuclease with affinity for inosine which is the deamination product of adenosine. The genomes of most organisms, including human, encode ENDOV homologs, yet knowledge about in vivo functions and gene regulation is sparse. To contribute in this field, we analyzed mRNA and protein expression of human ENDOV (hENDOV). Analyses of public sequence databases revealed numerous hENDOV transcript variants suggesting extensive alternative splicing. Many of the transcripts lacked one or more exons corresponding to conserved regions of the ENDOV core domain, suggesting that these transcripts do not encode for active proteins. Three complete transcripts were found with open reading frames encoding 282, 308 and 309 amino acids, respectively. Recombinant hENDOV 308 and hENDOV 309 share the same cleavage activity as hENDOV 282 which is the variant that has been used in previous studies of hENDOV. However, hENDOV 309 binds inosine-containing RNA with stronger affinity than the other isoforms. Overexpressed GFP-fused isoforms were found in cytoplasm, nucleoli and arsenite induced stress granules in human cells as previously reported for hENDOV 282. RT-qPCR analysis of the 3'-termini showed that hENDOV 308 and hENDOV 309 transcripts are more abundant than hENDOV 282 transcripts in immortalized cell lines, but not in primary cells, suggesting that cells regulate hENDOV mRNA expression. In spite of the presence of all three full-length transcripts, mass spectrometry analyses identified peptides corresponding to the hENDOV 309 isoform only. This result suggests that further studies of human ENDOV should rather encompass the hENDOV 309 isoform.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing*
  • Cell Line
  • Deoxyribonuclease (Pyrimidine Dimer) / genetics*
  • Humans
  • Protein Isoforms
  • RNA, Messenger / genetics*
  • Viral Proteins / genetics*

Substances

  • Protein Isoforms
  • RNA, Messenger
  • Viral Proteins
  • endonuclease V, phage T4
  • Deoxyribonuclease (Pyrimidine Dimer)

Grants and funding

This study was supported by grants to IA from The Norwegian Cancer Society (Grant number 5739724), The Norwegian Research Council (Grant number 250474) and Health Authority South East (Grant number 2017088). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.