Comparative genomic analysis of eutherian interferon genes

A Novel Inactive Isoform with a Restored Reading Frame Is Expressed from the Human Interferon Lambda 4 TT Allele at rs368234815

The TT allele of the dinucleotide variant rs368234815 (TT/ΔG) abolishes the open reading frame (ORF) created by the ancestral ΔG allele of the human interferon lambda 4 (IFNL4) gene, thus preventing the expression of a functional IFN-λ4 protein. While probing the expression of IFN-λ4 in human peripheral blood mononuclear cells (PBMCs), using a monoclonal antibody that binds to the C-terminus of IFN-λ4, surprisingly, we observed that PBMCs obtained from TT/TT genotype individuals could also express proteins that reacted with the IFN-λ4-specific antibody. We confirmed that these products did not emanate from the IFNL4 paralog, IF1IC2 gene. Using cell lines and overexpressing human IFNL4 gene constructs, we obtained evidence from Western blots to show that the TT allele could express a protein that reacted with the IFN-λ4 C-terminal-specific antibody. It had a molecular weight similar if not identical to IFN-λ4 expressed from the ΔG allele. Furthermore, the same start and stop codons used by the ΔG allele were used to express the novel isoform from the TT allele suggesting that a restoration of the ORF had occurred in the body of the mRNA. However, this TT allele isoform did not induce any IFN-stimulated gene expression. Our data do not support a ribosomal frameshift that leads to the expression of this new isoform, implying that an alternate splicing event may be responsible. An N-terminal-specific monoclonal antibody did not react with the novel protein isoform suggesting that the alternate splicing event likely occurs beyond exon 2. The new isoform is glycosylated similar to the functional IFN-λ4 and is also secreted. Furthermore, we show that the ΔG allele can also potentially express a similarly frameshifted isoform. The splicing event that leads to the generation of these novel isoforms and their functional significance remains to be elucidated.

Revised eutherian gene collections

Objectives

The most recent research projects in scientific field of eutherian comparative genomics included intentions to sequence every extant eutherian species genome in foreseeable future, so that future revisions and updates of eutherian gene data sets were expected.

Data description

Using 35 public eutherian reference genomic sequence assemblies and free available software, the eutherian comparative genomic analysis protocol RRID:SCR_014401 was published as guidance against potential genomic sequence errors. The protocol curated 14 eutherian third-party data gene data sets, including, in aggregate, 2615 complete coding sequences that were deposited in European Nucleotide Archive. The published eutherian gene collections were used in revisions and updates of eutherian gene data set classifications and nomenclatures that included gene annotations, phylogenetic analyses and protein molecular evolution analyses.