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PRR16
PRR16 is a protein that in Homo sapiens is encoded by the PRR16 gene. The protein has been shown to have an correlation with increased cell size and cancer. The protein has also been shown to have increased expression in the offspring of obese mothers. Orthologs have been found across vertebrates.

Gene
The gene PRR16  is also known as DZC54, LARGEN and mesenchymal stem cell protein. The gene is found on chromosome 5, a diagram of the gene neighborhood can be seen below  The PRR16 gene spans a length of 330,366 bp on chromosome 5.

mRNA
The human PRR16 gene is transbribed into a mRNA with 1754 base pairs. The start codon is at base pair 210 and the stop codon is at base pair 1124. The 5’ UTR and the 3’ UTR surround this open reading frame upstream and downstream respectively. An intron splice site is at base pair 368. Finally, a upstream stop codon can be found at bp 132. See annotated translation.

Four mRNA variants are observed for the PRR16 gene. All variants contain a shared 3' exon, see stared exon within the mRNA variants. Variant 1 encodes the longest protein isoform and is the most common. The variants 3 and 4 contain alternate 5’ exons. They both code for isoform 2. These proteins both begin translation at a downstream start codon, see annotated translation and mRNA variants. The final variant, variant 4, also contains an alternative 5 exon, however, in this case the exon provides an different start codon for the protein. See mRNA varients.

Transcript Variant 1 Transcript Variant 3 Transcript Variant 4 Transcript Variant 2

Protein
Isoform 1 of the PRR16 protein has a molecular weight of 33 kD. The isoelectric point of the protein is 9.2. This protein is proline rich containing nearly three times the normal proline concentration. The concentration of Tyrosine, Tryptophan and Phenylalanine in this protein is lower than average.

Post transnational modifications on the protein include phosphorylation. Phosphorylation is predicted at many different sites within the protein. The most reliable predictions place phosphorylation sites at amino acids 5, 75, 83, 91, 130, and 299. Additionally, the protein is predicted to be acetylated at the N-terminus.

The secondary structure of the protein is highly conserved over orthologs. Orthologs show a alpha helix at approximately amino acid 50 as well as a pleated sheet at about 10 amino acids away from the C-terminus.

Expression
The expression of PRR16 has been determined to be primarily cytosolic. In humans the PRR16 gene is expressed in a wide range of tissues. Strong expression is seen in the bone, brain, heart, placenta, pineal body and spleen, while weaker expression can be seen in the muscle, eye, liver prostate and skin.

Regulation of Expression
Here we see a comparison between two groups of mice both displaying prostate cancer. After surgical castration one of the groups showed much lower expression of PRR16 within tumor cells. This group also showed reduced tumor size, however this correlation is not necessarily causal. This suggests that PRR16 expression is influenced by hormone levels. Here a healthy donor supplied the tissue and cancer is not a contributing factor. The figure suggests that the protein is expressed at higher levels under hypoxic conditions.

Protein-Protein Interactions
Suggested Interactions determined by two hybrid assays and confirmed by multiple sources.
 * APP
 * Amyloid Precursor protein
 * NEDD4, NEDD4L and SMURF1
 * Ubiquitination family of proteins
 * PPP1CA
 * Serine Threonine specific phophatase
 * ABI2
 * Abelson Interactor

Clinical Significance
PRR16 has been shown to correlate positively with mammal cell size.

Paralogs
There are no paralogs of PRR16.

Orthologs
Orthologs of the PRR16 gene are found throughout bony organisms. A limited description of the ortholog space can be seen in the attached image. The conserved regions represented in the annotated translation of the PRR16 gene are seen throughout the ortholog space. The conservation of these regions indicate that they contain some necessary function for the organisms. This function remains unidentified. The protein conservation is consistent with highly conserved proteins such as cytochrome-c. Orthologs can be visualized in the chart below.