A Conserved Leucine Zipper Motif in Gammaherpesvirus ORF52 Is Critical for Distinct Microtubule Rearrangements.

Productive viral infection often depends on the manipulation of the cytoskeleton. Herpesviruses, including rhesus monkey rhadinovirus (RRV) and its close homolog, the oncogenic human gammaherpesvirus Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV8), exploit microtubule (MT)-based retrograde transport to deliver their genomes to the nucleus. Subsequently, during the lytic phase of the life cycle, the maturing viral particles undergo orchestrated translocation to specialized regions within the cytoplasm, leading to tegumentation, secondary envelopment, and then egress. As a result, we hypothesized that RRV might induce changes in the cytoskeleton at both early and late stages of infection. Using confocal imaging, we found that RRV infection led to the thickening and acetylation of MTs emanating from the MT-organizing center (MTOC) shortly after viral entry and more pronounced and diffuse MT reorganization during peak stages of lytic gene expression and virion production. We subsequently identified open reading frame 52 (ORF52), a multifunctional and abundant tegument protein, as being the only virally encoded component responsible for these cytoskeletal changes. Mutational and modeling analyses indicated that an evolutionarily conserved, truncated leucine zipper motif near the N terminus as well as a strictly conserved arginine residue toward the C terminus of ORF52 play critical roles in its ability to rearrange the architecture of the MT cytoskeleton. Taken together, our findings combined with data from previous studies describing diverse roles for ORF52 suggest that it likely binds to different cellular components, thereby allowing context-dependent modulation of function.IMPORTANCE A thorough understanding of the processes governing viral infection includes knowledge of how viruses manipulate their intracellular milieu, including the cytoskeleton. Altering the dynamics of actin or MT polymerization, for example, is a common strategy employed by viruses to ensure efficient entry, maturation, and egress as well as the avoidance of antiviral defenses through the sequestration of key cellular factors. We found that infection with RRV, a homolog of the human pathogen KSHV, led to perinuclear wrapping by acetylated MT bundles and identified ORF52 as the viral protein underlying these changes. Remarkably, incoming virions were able to supply sufficient ORF52 to induce MT thickening and acetylation near the MTOC, potentially aiding in the delivery viral genomes to the nucleus. Although the function of MT alterations during late stages of infection requires further study, ORF52 shares functional and structural similarities with alphaherpesvirus VP22, underscoring the evolutionary importance of MT cytoskeletal manipulations for this virus family.

Vasectomy influences expression of HE1 but not HE2 and HE5 genes in human epididymis.

Epididymal roles include protection and transport, maturation, and storage of the sperm cells. It is known that these functions are altered under vasectomy, but the consequences of excurrent duct obstruction on the pattern of gene expression along the human epididymis are poorly documented. In order to understand how excurrent duct occlusion affects different epididymal regions, the expression pattern of genes known to be expressed in specific epididymal segments was investigated along the epididymides of vasectomized men. Selected human epididymal complementary DNAs (cDNAs) identified by differential library screening were studied because of their unique messenger RNA (mRNA) distribution along the different epididymal segments. In situ hybridization as well as immunohistologic studies were undertaken to investigate the effect of vasectomy on a gene expressed all along the epididymis (HE1) or more selectively in the proximal (HE2) or distal (HE5) segment. The HE1 transcript was affected by the obstruction of the epididymis with little or no mRNA detectable along the epididymis. The HE1-related antigen was shown by immunohistochemical methods to be reduced within the epithelium of the epididymis of vasectomized men. By contrast, HE5 mRNA and protein, expressed in epithelial cells of the distal epididymis, were not affected by the obstruction of the vas deferens. Similarly, HE2 transcriptional and translational products normally expressed in the caput epididymidis were not affected by vasectomy. These results show that excurrent duct obstruction differentially affects the expression pattern of some specific transcripts and their encoded proteins, probably impairing their fundamental roles in the physiology of the epididymis.