Effect of adenovirus on metabolism of specific host mRNAs: transport control and specific translational discrimination.

Abstract

We have studied the adenovirus-induced inhibition of host cell protein synthesis and the effect of infection on the overall metabolism of host cell mRNA during the late phase of adenovirus infection by following the fate of a number of cellular mRNAs complementary to specific cloned DNA segments. At a time in infection when the rate of total cellular protein synthesis is drastically (>90%) reduced, transcription of specific cellular genes is undiminished. However, the transport of newly synthesized cellular mRNA to the cytoplasm is greatly decreased. This decreased appearance of new mRNA in the cytoplasm cannot account for the observed cessation of cell specific protein synthesis, however, since the concentration of several preexisting cellular mRNAs, including the mRNA for actin, remains unchanged throughout the course of infection. The preexisting mRNA is intact, capped, and functional as judged by its ability to direct protein synthesis in vitro in a cap-dependent fashion. The interruption in host translation appears to operate at the level of initiation directly, since we find that fewer ribosomes are associated with a given cellular mRNA after infection than before infection. Furthermore, the in vivo inhibition of cellular protein synthesis does not appear to be the result of competition with viral mRNA, since conditions which prevent the efficient initiation of translation of viral mRNA (infection with a viral mutant) do not result in the recovery of cell translation. Thus, it appears that a late adenovirus gene product directly mediates a shutoff of host protein synthesis.The interaction of a virus with its host cell often leads to an alteration in the synthesis and metabolism of macromolecules in the cell. The study of these alterations offers the opportunity to gain information concerning the normal course of events within the cell. For example, many different cytolytic virus infections result in decreased host protein synthesis at the same time that viral protein synthesis increases (22). The molecular basis for this viral "takeover" is best understood for poliovirus (9,19,39,42) and reovirus (33) infections, where differentiation between capped and uncapped mRNAs allows discrimination between viral and host mRNAs. However, the long-standing observation that host protein synthesis is greatly depressed late in adenovirus infection (2, 4, 5) cannot be easily explained; adenovirus mRNAs are all capped (12,23,35,45) and polyadenylated [poly(A)+] (28) and therefore would appear to be indistinguishable from host mRNAs on a gross level (6,32). Virtually all of the newly labeled mRNA that reaches the polyribosomes is virus specific (5,20,27), suggesting that transcription of cellular genes may be inhibited. However, neither the rate of synthesis of specific cellular mRNAs nor the fate of preexisting cellular mRNA has been examined with cloned cell DNA sequences.Beltz and Flint (5) approached the question of host cell mRNA manufacture and host protein synthesis by using cDNA hybridization to total cellular mRNA...

Adenovirus type 2 activates cell cycle-dependent genes that are a subset of those activated by serum.

“…Our data show that the RNA levels do increase. The difference between TK (where both activity and RNA levels are increased) and ODC (increased RNA levels but no increase in activity) is an intriguing hint of the complexity of the regulation of gene expression in adenovirus-infected cells and supports the translation discrimination proposed by Babich et al (4). Khalili and Weinmann (36) have analyzed the metabolism of actin mRNA in permissive HeLa cells after adenovirus infection.…”

“…All of the sequences tested increased in amounts after serum stimulation. The expression of c-myc, 4F1, 2F1, and KC-1 (the last not shown) increased within 4 (31). The expression of 2A9, ODC (Fig.…”

“…In the first place, it is important to make the distinction between our data in nonpermissive or semipermissive cells from those that are obtained in permissive cells, where inhibition of macromolecular synthesis is the rule, at least by 24 h postinfection (8,56), although exceptions occur (4,50,70). At any rate, the effect of adenovirus infection on gene expression in permissive cells has been already discussed in several papers (15,16,23,36,40).…”

Degradation of cellular mRNA during influenza virus infection: its possible role in protein synthesis shutoff

“…Picornaviruses and vesicular stomatitis virus inhibit RNA polymerase II activity (Crawford et al, 1981 ;McGowan et al, 1982). Adenoviruses block the cellular mRNA nucleocytoplasmic transport (Babich et al, 1983). Herpesviruses and poxviruses induce the degradation of pre-existing cellular mRNAs (Nishioka & Silverstein, 1978;Rice & Roberts, 1983), Finally, viruses alter the cell translational machinery by several different means.…”

Structure and expression of the human gene encoding major heat shock protein HSP70.

“…The dephosphorylation reaction was quenched with an equal volume of 10 mM Tris-hydrochloride (pH 8.0)-0.1 M NaCl-1 mM EDTA-0.5% SDS, heated to 68°C for 15 min, and extracted with phenol-chloroform (1:1). The 5' termini were phosphorylated with [y-32P]ATP (3,000 Ci/mmol; Amersham) and T4 polynucleotide kinase (44). Unincorporated nucleotides were removed by Sephadex G-50 chromatography.…”