Biochemical and Genetical Characterization of a Fiber-Defective Temperature-Sensitive Mutant of Type 2 Adenovirus

The EMBO Joumal Vol.2 No.11 pp.1921-1927, 1983 Biochemical and genetical characterization of a fiber-defective temperature-sensitive mutant of type 2 adenovirus Marie-Laure Boudin, Muriel Rigolet1, Pierre Lemay, fiber structure: the fiber polypeptide unit (polypeptide IV) is Francis Galibert1 and Pierre Boulanger* of lower apparent mol. wt. in SDS-polyacrylamide gel than Laboratoire de Virologie Moleculaire de l'INSERM (U. 233), Place de Ver- the WT fiber polypeptide unit (D'Halluin et al., 1980). A fur- dun, 59045 Lille CUdex, and 'Laboratoire d'Hematologie Experimentale, ther biochemical characterization of the H2 ts 125 is Centre Hayem, H6pital Saint Louis, 75475 Paris C&dex 10, France presented here, and the genetical lesion determined by DNA Communicated by P. Boulanger sequencing of the mutant fiber gene. Received on 27 June 1983; revised on 29 July 1983 The adenovirus type 2 fiber mutant H2 ts 125 synthesized an Results unstable, temperature-sensitive fiber polypeptide with an ap- Synthesis, post-translational modifications and virion incor- parent mol. wt. smaller by 2500 than the wild-type (62 K). poration offiber in H2 ts 125 mutant The polypeptide of 59.5 K was found to be stable at the per- Synthesis offiber polypeptide in H2 ts 125 infected-cells missive temperature (33°C). H2 ts 125 fiber synthesized in and virion incorporation. KB cells were infected with WT or reticulocyte lysates had the same apparent mol. wt. of 59.5 K H2 ts 125 at 10 f.f.u./cell at 39.5°C and pulse-labeled for 1 h as the mutant fiber produced in vivo. Neither structural nor at 16 h after infection. The cell culture was then divided into functional differences between wild-type and mutant fibers two portions, one being harvested just after the pulse, the were detected in the N-terminal and C-terminal sequences, ex- other one being chased for 8 h at 39.5°C. Virus-coded poly- cluding the occurrence of a new initiation or termination peptides were analyzed by SDS-polyacrylamide gel electro- codon. Restriction analysis of H2 ts 125 DNA also ruled out phoresis (PAGE). Figure IA shows that in the H2 ts 125 pat- the hypothesis of a deletion mutant. The 59.5 K mutant fiber tern at 39.5°C, the apparent mol. wt. of the fiber polypeptide unit was normally glycosyated, N-acetylated, assembled into (IV) was 2500 lower than that in the WT. Careful determina- 6S oligomeric fiber and incorporated into virions. DNA se- tion by electrophoresis in 30-cm slab gels with mol. wt. stan- quencing of the H2 ts 125 fiber gene revealed two point muta- dards (Pharmacia LMW calibration kit) gave the value of tions at nucleotides 3970 (C*TT-T*TT) and 4958 59 500 for H2 ts 125 fiber, instead of 62 000 for WT fiber (GC*T-GT*T), corresponding to two amino acid changes at (theoretical value: 61 882; Herisse et al., 1981). The label in positions 105 and 434, respectively. The 105 mutation con- sisted of a conservative change Leu-Phe; the 434 inter- change was Ala-Val, usually considered as non- 4- conservative. Th possibility of a donor site for splicing created by the mutation at codon GTT was eliminated on the basis of Si nuclease analysis data. All these results suggested that either one or both mutations concerned highly organized domain(s) of the fiber polypeptide chain, resulting in aberrant mobility in SDS-polyacrylamide gels and temperature- sensitivity. Key words: adenovirus 2/fiber protein/DNA sequence/fiber .. 595k gene/ts mutants Introduction Sets of temperature-sensitive (ts) mutants of adenoviruses have been selected in several laboratories to determine the role of adenovirus gene products involved in viral replication and morphogenesis, as well as to study various aspects of the virus-cell interactions (reviewed by Ginsberg and Young, 1977). The adenovirus 2 mutant H2 ts 125 has been isolated in our laboratory after mutagenization of a wild-type (WT) stock, and partially characterized (Martin et al., 1975). It is altered in the production of antigenically reactive fiber and accumulates light assembly intermediate particles (or top components) at the non-permissive temperature (D'Halluin et al., 1980: Martin et al., 1978). H2 ts 125 has been recently mapped between coordinates Fig. 1. SDS-polyacrylamide gel analysis of WT and mutant fiber polypep- 81 and 100 on the et a tides in cells and virions. (A) Pulse-chase experiments at 39.5°C. The cells genomic map (D'Halluin al., 1982), were labeled with [35S]methionine for 1 h at 16 h after infection. (p) 1 h position which overlaps the fiber gene (85.5-91.8 map units) pulse, (c) 8 h chase. (B) Stained gel (Coomassie blue) showing WT and (Miller et al., 1980). It has been found to be altered in the H2 ts 125 virus particles produced at the permissive temperature. In cells as well as in virion, the fiber polypeptide (IV) has an apparent mol. wt. of *To whom reprint requests should be sent. 62 000 in WT and 59 500 in H2 ts 125. © IRL Press Limited, Oxford, England. 1921 M.-L. Boudin et al. .., b- N&VAR 04-or"14. 1, ,VOW. 4mmum, A ': ni Ilia z4.-nl 36;-flnw "i i-.. i. 0to, .... i::"..: .1 .... -'. Fig. 2. SDS-polyacrylamide gel analysis of the post-translational modifications of the WT and mutant fibers. (A) Glycosylation. The WT-and Fig. 3. Cell-free translation of WT and H2 ts 125 late mRNAs. (v): control H2 ts 125-infected cells were labeled with [3H]glucosamine for 8 h at 16 h [14C]valine-labeled virion polypeptide markers. (a) WT mRNAs translated after infection. (v): control [3H]leucine-labeled virion; (h): [3H]leucine- in vitro in the presence of 2 mM MgCl2, 130 mM KCl; (b) H2 ts 125 labeled hexon marker; (wt): [3H]glucosamine-labeled wild-type extract; (ts): mRNAs with 3 mM MgCl2, 13 mM KCl; (c) H2 ts 125 mRNAs translated [3H]glucosamine-labeled H2 ts 125-mutant extract. (B) N-acetylation. WT- as in (a); (d) parotid gland collagen mRNAs used as control. and H2 ts 125-infected cells were labeled with [14C]sodium acetate for 24 h at 56 h after infection at 330C. (v): Control [14C]valine-labeled virion; (wt): WT-extract; (ts): H2 ts 125 extract. Gels A and B were revealed by fluoro- graphy at - 700C. the mutant fiber polypeptide migrated with an apparent mol. wt. of 59.5 K, instead of 62 K for the WT. 59.5 K polypeptide disappeared during the chase at 39.5°C. A shorter fiber polypeptide unit was also found incorporated in the H2 ts 125 virus particles assembled at the permissive temperature (Figure IB). Glycosylation of H2 ts 125 fiber. The hypothesis of a defect in the glycosylation process of the fiber protein at 39.5°C, which could result in a different electrophoretic migration (Leavitt et al., 1977; Persson et al., 1980), was ex- amined by labeling H2 ts 125-infected cells with [3H]glucosamine for 8 h at 16 h after infection. The fluorographic pattern of an SDS-polyacrylamide gel revealed that the major late glycoprotein was a 62 K species in the WT and a 59.5 K species in the H2 ts 125 (Figure 2A). N-acetylation of H2 ts 125 fiber. The possibility of an absence of N-acetylation of the fiber polypeptide chain, Fig. 4. Comparative carboxypeptidase digestions of WT and H2 ts 125 thereby rendering it sensitive to cellular aminopeptidase(s) fibers. Samples of purified [35S]methionine-labeled fiber were incubated was explored as follows. WT- and H2 ts 125-infected cells with carboxypeptidase (CP) A (A), carboxypeptidase B (B), a mixture of both carboxypeptidases A and B (A + B), carboxypeptidase Y (Y), or no were labeled with [14C]acetate for 24 h at 56 h after infection carboxypeptidase (0) and analyzed in SDS-gel. (wt): wild-type fiber' (ts): at 33°C or for 8 h at 16 h after infection at 39.5°C. The cells mutant fiber. The same type of carboxypeptidase-resistant core was obtain- were disrupted by sonication in hypotonic buffer (10 mM ed with single CPA, CPY or double CPA +CPB digestion: 60 K and Tris-hydrochloride, pH 7.5, 50 mM NaCl) and the cell ex- 57.5 K for WT and mutant fibers, respectively. Both types of fibers seemed insensitive to CPB action. v: control virion. tract centrifuged at 10 000 g for 60 min. The supernatant was analyzed by SDS-PAGE. As shown in Figure 2B, most of the primary translational products of WT adenovirus were acetylated 59.5 K was observed in place of the 62 K fiber N-acetylated: II, 100 K, III and IV appeared as the major polypeptide unit present in the WT, at either 39.5° or 33°C. 14C-acetylated adenovirus polypeptides; minor bands of [14C]- The H2 ts 125 polypeptide unit of 59 500 daltons was acetate-labeled IIIa, V, 39 K, pVI and pVIII were also visible. therefore normally N-acetylated. The H2 ts 125 fiber also In H2 ts 125-infected cell extract, a major species of 14C-N- showed the same resistance to aminopeptidase M digestion as 1922 Characterization of a fiber-defective ts mutant of adenovirus type 2 * ~ ~~~~~5- .-fm-_, Fig. 5. Assembly of penton base and mutant fiber in vitro. 2D pattern of H2 ts 125-infected cell extract maintained at 33°C and analyzed before (a) and after (b) addition of a large excess of unlabeled penton base.

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