The herpes simplex virus 1 U _L 41 gene-dependent destabilization of cellular RNAs is selective and may be sequence-specific

Abstract

In cells infected with herpes simplex virus 1, the RNA encoded by the stress-inducible immediate early response gene IEX-1 was up-regulated immediately after infection. However, the accumulated RNA was degraded 3 -5 , and the protein was detectable only at very early times after infection. The degradation was dependent on the U L41 gene encoding the virion host shutoff (vhs) protein and resulted in the accumulation of truncated RNA containing the 5 -end portion of the transcript. IEX-1 contains an AU-rich element (ARE) in its 3 -untranslated domains known to regulate negatively the RNA lifespan. To examine the role of ARE in signaling the degradation, we compared the stability of several RNAs up-regulated during infection to WT virus. These were ARE-containing RNAs encoding IEX-1, c-fos, and I B␣ and the non-ARE-containing RNAs GADD45␤ and tristetraprolin. We report that the AREcontaining RNAs exemplified by IEX-1 RNA are deadenylated and cleaved in the ARE within the 3 UTR in a U L41-dependent manner. In contrast, Northern blot hybridizations and analyses of poly(A) tails revealed no evidence of degradation of GADD45␤ RNA. O ne of the key early events in the replication of herpes simplex virus 1 (HSV-1) is the diminished incorporation of amino acids into cellular proteins. This process was mapped to a gene designated U L 41, and the protein product was designated virion host shutoff or vhs (1-3). vhs is an M r 58,000 polypeptide, which is packaged in the tegument of HSV virions, and its activity has been extensively investigated. The current model of vhs function is that, on infection, vhs is released into the cytoplasm and acts as an RNase in conjunction with the translational factor eIF4H (4). It has been reported that vhs degrades sequences near the 5Ј end of mRNA more rapidly than those at the 3Ј end (5). The nucleolytic activity of vhs is specific for mRNA. Host rRNA and tRNA are unaffected, whereas viral and host mRNAs are rapidly degraded. Because viral mRNA is transcribed at a higher rate than cellular mRNA, viral proteins do accumulate. At middle or late times after infection, vhs interacts with the ␣-trans-inducing factor also known as VP16 encoded by the U L 48 ORF and it becomes inactive (6). The function of vhs appears to be twofold, to enable efficient transition from ␣ to ␤ and ␥ protein synthesis and to block host responses to infection. Indeed, ⌬U L 41 mutants are more sluggish in their replication and replicate poorly in immunocompetent experimental animal systems (7).The problem addressed in this report stems from two observations. The first involved comparisons of host cell RNAs induced in WT virus-infected cells and in cells infected with a ⌬U L 41 mutant (8). The expectation was that the number of cellular genes whose transcripts would be up-regulated and the level of accumulated mRNAs in ⌬U L 41-mutant-infected cells would be vastly higher than those in WT virus-infected cells. This was not the case. The second observation involved a thorough analysis of one cellular RNA, encoded by the s...

The U L 41 protein of herpes simplex virus 1 degrades RNA by endonucleolytic cleavage in absence of other cellular or viral proteins

“…The results described above were in agreement with the pattern of degradation of IEX-1 mRNA observed in HSV-1-infected cells and specifically with the lingering of truncated 5Ј domains, generated by vhs-dependent endonucleolytic cleavage within the AREs (19,21). The objective of the experiments described in this section was to test whether a substrate, consisting of only IEX-1 coding sequence domain (CDS, substrate 3), was cleaved by the purified GST-vhs fusion protein.…”

“…Although we do not contest the conclusion that the vhsdependent degradation of some mRNAs initiates at or near the 5Ј terminus, studies carried out in our laboratory do not support the concept that vhs mediates indiscriminate degradation of mRNAs or that the degradation invariably proceeds 5Ј to 3Ј (19). Examination of the relative rates of degradation of several cellular mRNAs upon HSV-1 infection led to the conclusion that cellular RNAs form at least three classes based on their fate after infection.…”

“…Examination of the relative rates of degradation of several cellular mRNAs upon HSV-1 infection led to the conclusion that cellular RNAs form at least three classes based on their fate after infection. There are (i) constitutively expressed mRNAs (i.e., GAPDH, ␤-actin) that were rapidly degraded (20); (ii) some inducible mRNAs containing AU-rich elements (AREs) in their 3Ј UTR (i.e., stress-inducible immediate-early responsive gene or IEX-1, I B␣, c-fos) that were deadenylated, subjected to endonucleolytic cleavage near the 3Ј end and to 3Ј-to-5Ј degradation, with the 5Ј-truncated mRNA fragments persisting in wild-type virus-infected cells for many hours (20,21), and (iii) some inducible mRNAs, exemplified by GADD45␤ and tristetraprolin, which showed no evidence of degradation and whose proteins readily accumulated in infected cells (19,22). All of these processes require vhs because none of them was detected in cells infected with the ⌬U L 41-mutant virus.…”

Bovine herpesvirus 1 infection and infectious bovine rhinotracheitis

“…In BoHV-1 infected cells, the cellular protein synthesis is shut off in part by the vhs tegument protein [76,95]. By analogy to the HSV-1 UL41 encoded protein, the latter is supposed to degrade mRNA preexisting in the target cell [48,99]. Several studies were devoted to the regulation of apoptosis during productive BoHV-1 infection.…”

Viral-mediated stabilization of AU-rich element containing mRNA contributes to cell transformation

“…So far, several virus gene products, for example HSV UL41 (Esclatine et al, 2004) and KSHV KaposinB (McCormick and Ganem, 2001), have been shown to have the potential to control the fate of ARE-mRNA. In the late phase of adenovirus infection, although the export of the bulk of cellular mRNA is inhibited, ARE-mRNA is exported into the cytoplasm (Higashino et al, 2005).…”