Disease relevance of UL12

• To elucidate the role of US11 in the virus life cycle, we infected cells with wild-type virus, a cosmid-reconstructed US11 HSV-1 null mutant, and a cosmid-reconstructed wild-type virus and analyzed expression of UL12, -13, and -14 during a time course of infection [1].
• UL12 is a 5'- to 3'-exonuclease encoded by herpes simplex virus type 1 (HSV-1) which degrades single- and double-stranded DNA [2].
• The alkaline exonuclease (AE) encoded by the herpes simplex virus type 1 (HSV-1) UL12 open reading frame was inducibly expressed in Escherichia coli and purified without the use of chromatographic separation [3].
• Inactivation of the UL12 gene results in reductions in viral DNA synthesis, DNA packaging, egress of DNA-containing capsids from the nucleus and ability of progeny virions to initiate new cycles of infection [4].
• We constructed two point mutations in a highly conserved region (motif II) of UL12 and purified wild-type and mutant enzymes from a baculovirus expression system [5].

High impact information on UL12

• Herpes simplex virus type 1 single-strand DNA binding protein ICP8 enhances the nuclease activity of the UL12 alkaline nuclease by increasing its processivity [2].
• In vitro processing of herpes simplex virus type 1 DNA replication intermediates by the viral alkaline nuclease, UL12 [6].
• Our data suggest that UL12 functions at nicks and gaps in replicating DNA to correctly repair or process the replicating genome into a form suitable for encapsidation [6].
• Recently, an alternate open reading frame designated UL12.5 was identified within the UL12 gene [7].
• The UL12 open reading frame of herpes simplex virus type 1 (HSV-1) encodes a deoxyribonuclease that is frequently referred to as alkaline nuclease (AN) because of its high pH optimum [7].

Chemical compound and disease context of UL12

• Sucrose sedimentation analysis of capsids from cells infected with wild-type or mutant viruses indicates that both UL12 and UL12.5 are found in fractions from across the sucrose gradient which do not always correlate with the presence of viral capsids [8].

Biological context of UL12

• Although the precise in vivo role of UL12 has not yet been determined, several in vitro activities have been identified for the protein, including endo- and exonuclease activities, interaction with the HSV-1 single-stranded DNA binding protein ICP8, and an ability to promote strand exchange in conjunction with ICP8 [9].
• While the wild-type plasmid complements the growth of the null mutant, neither UL12 mutant can do so [5].
• We showed previously that the UL12.5 gene product cannot compensate for the absence of the full-length UL12 gene product (R. Martinez, L. Shao, J. C. Bronstein, P. C. Weber, and S. K. Weller, 1996, Virology 215, 152-164); however, it was not known whether UL12.5 itself performs an essential function during lytic viral growth [8].
• In this study, amplicons (bacterial plasmids containing functional copies of a virus replication origin and packaging signal) were used to analyse further the defects of the UL12 null mutant ambUL12 [4].
• In this report, we address the question of whether the AN-1 growth phenotype is due to the loss of UL12 catalytic activity [5].

Anatomical context of UL12

• Rabbit reticulocyte lysates programmed with wild-type UL12 RNA cleaved at the same sites cleaved by purified HSV-1 DNase, but distinct from those cleaved by DNase 1 or micrococcal nuclease [10].
• Expression of recombinant herpes simplex virus type 1 (HSV-1) deoxyribonuclease (DNase) was analyzed in BHK-21 cells, a standard cell line for virus propagation, by using mammalian cell expression systems based on vaccinia virus and on Semliki Forest virus (SFV)1 [11].

Associations of UL12 with chemical compounds

• UL12.5 and UL12 have the same translational stop codon, but the former utilizes an internal methionine codon of the latter gene to initiate translation of a 60-kDa amino-terminal truncated form of AN [7].

Other interactions of UL12

• Using complementing cells, we constructed HSV-1 mutants carrying nonsense mutations in an essential gene, UL8, encoding a protein essential for viral DNA replication (ambUL8) or in a partially dispensable gene, UL12, encoding alkaline nuclease (ambUL12) [12].

Analytical, diagnostic and therapeutic context of UL12

• Western immunoblotting showed that the virus ambUL12 produced full-length UL12 protein in SupD12 cells which yielded a level of 25.9% of the alkaline nuclease activity of the wt HSV-1 control [12].

References