Alternative titles; symbols
HGNC Approved Gene Symbol: OAZ3
Cytogenetic location: 1q21.3 Genomic coordinates (GRCh38) : 1:151,762,969-151,771,330 (from NCBI)
By searching databases for sequences similar to OAZ1 (601579) and OAZ2 (604152), followed by sequencing cDNAs, Ivanov et al. (2000) cloned mouse and human OAZ3, which they called AZ3. The cDNAs contain 2 partially overlapping ORFs, and the second and longest ORF (ORF2) lacks an appropriate initiation codon. Since the OAZ1 and OAZ2 transcripts encoding active full-length ODC (ODC1; 165640) antizymes incorporate a frameshift that fuses ORF1 with ORF2, Ivanov et al. (2000) suggested that translation of full-length OAZ3 is initiated from ORF1 and includes a frameshift that fuses ORF1 to ORF2. In this model, the predicted human and mouse OAZ3 proteins contain 187 and 195 amino acids, respectively, and share 86% identity. Human OAZ3 shares 31% and 29% amino acid identity with OAZ1 and OAZ2, respectively. Northern blot analysis of 16 human tissues detected a 1.1-kb OAZ3 transcript in testis only. Overexposure suggested much weaker expression in prostate. In situ hybridization of adult mouse testis detected Oaz3 in developing spermatids upon appearance of proacrosomal granules, with prominent expression in the head cap. Expression decreased during late spermatid phase, and was absent from spermatozoa, as well as from Leydig cells, Sertoli cells, and vasculature. Phylogenetic analysis of eukaryotic antizyme proteins suggested that mammalian OAZ3 diverged from OAZ1 and OAZ2 early in vertebrate evolution.
By mass spectrometry, Ruan et al. (2011) found that endogenous and recombinant rat Oaz3 protein, which they called p12, was translated from a CUG codon upstream of the first AUG codon of ORF1. The protein contains 85 amino acids. Ruan et al. (2011) found no evidence for a frameshift fusing ORF1 with ORF2. Immunohistochemical analysis and immunoelectron microscopy of mouse testis and epididymis revealed that Oaz3 localized to outer dense fibers and fibrous sheath of the tail and to the connecting piece linking head and tail. Database analysis revealed orthologs of p12 only in mammals.
In OAZ1 and OAZ2, the short upstream ORF functions as a polyamine sensor that induces a frameshift in the OAZ transcript that leads to expression of the functional antizyme. Ivanov et al. (2000) engineered a frameshift in the mouse Oaz3 cDNA by deleting U in the stop codon of ORF1, fusing ORF1 with ORF2. The expressed Oaz3 protein, like Oaz1, inhibited Odc activity following expression in a mouse proximal tubule cell line.
Ruan et al. (2011) found that, unlike Oaz1, rat p12 did not inhibit coexpressed ODC following transfection in HEK293 cells. Yeast 2-hybrid analysis of rat testis proteins revealed that p12 interacted with Mypt3 (PPP1R16A; 609172). Immunohistochemical analysis showed that expression of p12 and Mypt3 overlapped in sperm tail. Cotransfection experiments revealed that binding to p12 resulted in accumulation of Mypt3 in a punctate cytoplasmic distribution away from the membrane. Mutation of ankyrin (see 612641) domain-2 of Mypt3 abrogated the interaction of Mypt3 with p12. Mypt3 also interacted with sperm tail PP1-gamma-2 (see PPP1CC; 176914), which reduced stress fiber formation when expressed alone in transfected mouse fibroblasts. Ruan et al. (2011) found that Mypt3 elevated stress fiber formation by inhibiting PP1-gamma-2, and that p12 disrupted Mypt3-PP1-gamma-2 complexes and counteracted the inhibitory effect of Mypt3.
Hartz (2011) mapped the OAZ3 gene to chromosome 1q21.2 based on an alignment of the OAZ3 sequence (GenBank AF175296) with the genomic sequence (GRCh37).
Tokuhiro et al. (2009) obtained Oazt -/- mice in the expected mendelian ratio. Oazt -/- animals appeared normal, and concentrations of polyamines in testis and sperm of Oazt -/- males were not affected. Oazt -/- females and Oazt +/- males showed normal fertility, whereas Oazt -/- males were infertile. Histologic and electron microscopic analysis of Oazt -/- testis showed normal morphology, with apparently normal germ cell development through to the elongated spermatid stage. However, mature spermatozoa in the cauda epididymis showed separated head and tail sections, with separation between the basal plate and capitulum accompanied by plasma membrane that sealed both stumps. Headless tails showed normal energetic swimming in culture medium, but isolated heads showed no acrosome reaction following calcium stimulation. Mutant sperm were not able to fertilize eggs by in vitro fertilization assays, but they produced healthy pups when transferred to oviducts of pseudopregnant females.
Hartz, P. A. Personal Communication. Baltimore, Md. 10/28/2011.
Ivanov, I. P., Rohrwasser, A., Terreros, D. A., Gesteland, R. F., Atkins, J. F. Discovery of a spermatogenesis stage-specific ornithine decarboxylase antizyme: antizyme 3. Proc. Nat. Acad. Sci. 97: 4808-4813, 2000. [PubMed: 10781085] [Full Text: https://doi.org/10.1073/pnas.070055897]
Ruan, Y., Cheng, M., Ou, Y., Oko, R., van der Hoorn, F. A. Ornithine decarboxylase antizyme Oaz3 modulates protein phosphatase activity. J. Biol. Chem. 286: 29417-29427, 2011. [PubMed: 21712390] [Full Text: https://doi.org/10.1074/jbc.M111.274647]
Tokuhiro, K., Isotani, A., Yokota, S., Yano, Y., Oshio, S., Hirose, M., Wada, M., Fujita, K., Ogawa, Y., Okabe, M., Nishimune, Y., Tanaka, H. OAZ-t/OAZ3 is essential for rigid connection of sperm tails to heads in mouse. PLoS Genet. 5: e1000712, 2009. Note: Electronic Article. [PubMed: 19893612] [Full Text: https://doi.org/10.1371/journal.pgen.1000712]