OSER1 (Oxidative Stress Responsive Serine Rich 1), or Chromosome 20 open reading frame 111, C20orf111, is the hypothetical protein that in humans is encoded by the OSER1gene.[5] OSER1/C20orf111 is also known as Perit1 (peroxide inducible transcript 1), HSPC207, and dJ1183I21.1.[6] It was originally located using genomic sequencing of chromosome 20.[7] The National Center for Biotechnology Information, or NCBI,[5] shows that it is located at q13.11 on chromosome 20, however the genome browser at the University of California-Santa Cruz (UCSC) website[8] shows that it is at location q13.12, and within a million base pairs of the adenosine deaminase locus.[9] It was also found to have an increase in expression in cells undergoing hydrogen peroxide(H 2O 2)-induced apoptosis.[10] After analyzing the amino acid content of OSER1, it was found to be rich in serine residues.
OSER1 a valid, protein coding gene that is found on the minus strand of chromosome 20 at q13.12 by searching the UCSC Genome Browser,[8] but q13.11 according to Refseq on NCBI.[5]
Gene neighborhood
A few of the known genes near OSER1 are given in the box below with their known function.
Help facilitate the assembly of DHPR with other proteins of the excitation-contraction coupling machinery. Loss of function leads to cardiac-specific JPH2 deficiency and results in lower cardiac contractility[11]
Encodes an enzyme that catalyzes the hydrolysis of adenosine to inosine. Deficiency in this enzyme causes a form of severe combined immunodeficiency disease (SCID), in which there is dysfunction of both B and T lymphocytes with impaired cellular immunity and decreased production of immunoglobulins.[13]
10 splice isoforms that encode good proteins, altogether 8 different isoforms, 2 of which are complete isoforms. The image below shows the 10 isoforms that are predicted.[15] Of these 10 splice isoforms, 8 have varying peptide lengths, however all of these proteins are only hypothetical with no extensive research done on them.[15]
Transcription regulation
When looking at the predicted promoter sequence,[16] there are no RNA Polymerase II binding sites, however there is a binding site for core promoter element for TATA-less promoters.[17] In this same region of the promoter, there is also a TATA-binding factor sequence, which helps in the positioning of RNA polymerase II for transcription.[18]
The function of OSER1 is not well understood by the scientific community in general. It does contain a domain of unknown function, DUF776, which has a large segment that is well conserved from Caenorhabditis elegans to humans.[21] Its expression is increased in rat cardiomyocytes undergoing hydrogen peroxide induced apoptosis.[10] It has also been shown that its overexpression extends lifespan in silkworms, nematodes, and flies, while its depletion correspondingly shortens lifespan.[21] This effect might be due to its regulation of mitochondrial biology and oxidative stress.[21] Moreover, it promotes reproduction in animal models and is associated with human reproduction and longevity.[21]
Expression
When looking at the EST Profiles in humans, normal tissue (non-cancerous), expresses at a level of 82 transcripts per million.[22] OSER1 has been shown to increase in expression in rat cardiac myocytes undergoing |H|2|O|2|-induced apoptosis, suggesting a role in cell death.[10] In bladder, cervical, head and neck, non-neoplasia, pancreatic, and prostate cancer cells, there are expression levels lower than normal.[citation needed]
Expression of Perit1 in cancerous cells according to NCBI Geo Profiles.
Homology
OSER1 gene has no clear paralogs in the human genome. However, it has many orthologs in other organisms, and is conserved highly in organisms such as Xenopus tropicalis and is semi-conserved in the proto-animal Trichoplax adherens at the C-terminus.
The following table presents a select number of the orthologs found.[23]
The image below is a multiple sequence alignment comparing the conservation of the OSER1 protein amongst other organisms. The protein is highly conserved in the DUF776 region amongst vertebrates, and also at the C-terminus in eukaryotes.
MSA of the orthologs of OSER1 protein
Predicted post-translational modification
C20orf111 protein schematic showing predicted secondary structure and post-translational modifications.
PELE (Protein Secondary Structure Prediction) was used to predict the secondary structure of OSER1. There is little in the way of β-strand or α-helix secondary structure, but a large part of the protein appears to exist as random coils. This is shown on the image of the OSER1 images to the right.
↑ Chang WC, Lee TY, Shien DM, Hsu JB, Horng JT, Hsu PC, Wang TY, Huang HD, Pan RL (November 2009). "Incorporating support vector machine for identifying protein tyrosine sulfation sites". J Comput Chem. 30 (15): 2526–37. doi:10.1002/jcc.21258. PMID19373826. S2CID16311112.
↑ Blom N, Gammeltoft S, Brunak S (December 1999). "Sequence and structure-based prediction of eukaryotic protein phosphorylation sites". J. Mol. Biol. 294 (5): 1351–62. doi:10.1006/jmbi.1999.3310. PMID10600390.
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