Structure function analysis of the HSV-1 UL52 zinc finger domain

The HSV-1 helicase-primase is a trimeric complex consisting of the products from UL5, UL8 and UL52 genes. These genes are essential for HSV-1 DNA replication and perform many functions during the viral DNA replication process. UL5 is believed to be the helicase based on the presence of seven conserved helicase motifs, UL8 has no known enzymatic activities, while UL52 is believed to be the primase subunit of the complex. UL52 contains a conserved primase catalytic domain found in both primases and polymerases. It also contains a zinc finger domain similar to those observed in prokaryotic and eukaryotic primases. This primase domain is highly conserved among members of the herpesviridae, and in our genetic and biochemical analyses of the zinc finger motif we determined it to be required not only for the primase activity of the helicase-primase complex, but also the helicase, ATPase and DNA binding activities of the complex. The data obtained in our study also show that polymerase recruitment to the replication fork is dependent on the UL52 subunit as mutations in either the catalytic site or the zinc binding domain result in the inefficient recruitment of the HSV-1 polymerase, UL30, to replication intermediates. We hypothesize based on the results of this study that the UL52 zinc finger domain is likely a DNA binding domain that is essential for the functions of the entire helicase-primase complex.

Mutations in the Putative Zinc-Binding Motif of UL52 Demonstrate a Complex Interdependence between the UL5 and UL52 Subunits of the Human Herpes Simplex Virus Type 1 Helicase/Primase Complex

Herpes simplex virus type 1 (HSV-1) encodes a heterotrimeric helicase-primase (UL5/8/52) complex. UL5 contains seven motifs found in helicase superfamily 1, and UL52 contains conserved motifs found in primases. The contributions of each subunit to the biochemical activities of the complex, however, remain unclear. We have previously demonstrated that a mutation in the putative zinc finger at UL52 C terminus abrogates not only primase but also ATPase, helicase, and DNA-binding activities of a UL5/UL52 subcomplex, indicating a complex interdependence between the two subunits. To test this hypothesis and to further investigate the role of the zinc finger in the enzymatic activities of the helicase-primase, a series of mutations were constructed in this motif. They differed in their ability to complement a UL52 null virus: totally defective, partial complementation, and potentiating. In this study, four of these mutants were studied biochemically after expression and purification from insect cells infected with recombinant baculoviruses. All mutants show greatly reduced primase activity. Complementation-defective mutants exhibited severe defects in ATPase, helicase, and DNA-binding activities. Partially complementing mutants displayed intermediate levels of these activities, except that one showed a wild-type level of helicase activity. These data suggest that the UL52 zinc finger motif plays an important role in the activities of the helicase-primase complex. The observation that mutations in UL52 affected helicase, ATPase, and DNA-binding activities indicates that UL52 binding to DNA via the zinc finger may be necessary for loading UL5. Alternatively, UL5 and UL52 may share a DNA-binding interface

A Summary of The Second Annual HIV Microbiome Workshop.

Commensal organisms appear to play significant roles in normal homeostasis as well as in the pathogensis of HIV infection in a number of different organ systems. On November 17th and 18th 2016, leading researchers from around the world met to discuss their insights on advances in our understanding of HIV and the microbiome at the NIH in Bethesda

A summary of the fourth annual Virology Education HIV Microbiome workshop.

Each year, a growing international collection of researchers meets at the NIH to share and discuss developments in the microbiome HIV story. This past year has seen continued progress toward a detailed understanding of host-microbe interactions both within and outside the field of HIV. Commensal microbes are being linked to an ever-growing list of maladies and physiologic states, including major depressive disorder, chronic kidney disease, and Parkinson disease. PubMed citations for "microbiome" are growing at an exponential rate with over 11,000 in 2018. Various microbial taxa have been associated with HIV infection, and some of these taxa associated with HIV infection have also been associated with systemic markers of inflammation in HIV infected individuals. Causality remains unclear however as environmental and behavioral factors may drive HIV risk, inflammation, and gut enterotype. Much of the work currently being done addresses potential mechanisms by which gut microbes influence immune and inflammatory pathways. No portion of the microbiome landscape has grown as rapidly as study of the interplay between gut microbes and response to cancer immunotherapy. As Dr. Wargo discussed in her keynote address, this area has opened the door to better understanding on how commensal microbes interact with the human immune system

Research capacity. Enabling the genomic revolution in Africa.

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