Biochemical studies on adenovirus multiplication, xi. Evidence of a cytoplasmic site for the synthesis of viral-coded proteins

Transport of viral RNA in kb cells infected with adenovirus type 2

Messenger RNA transport was studied in KB cells infected with the nuclear DNA virus adenovirus type 2. Addition of 0.04 µg/ml of actinomycin completes the inhibition of ribosome synthesis normally observed late after infection and apparently does not alter the pattern of viral RNA synthesis: Hybridization-inhibition experiments indicate that similar viral RNA sequences are transcribed in cells treated or untreated with actinomycin. The polysomal RNA synthesized during a 2 hr labeling period in the presence of actinomycin is at least 60% viral specific. Viral messenger RNA transport can occur in the absence of ribosome synthesis. When uridine-³H is added to a late-infected culture pretreated with actinomycin, viral RNA appears in the cytoplasm at 10 min, but the polysomes do not receive viral RNA-³H until 30 min have elapsed. Only 25% of the cytoplasmic viral RNA is in polyribosomes even when infected cells have been labeled for 150 min. The nonpolysomal viral RNA in cytoplasmic extracts sediments as a broad distribution from 10S to 80S and does not include a peak cosedimenting with 45S ribosome subunits. The newly formed messenger RNA that is ribosome associated is not equally distributed among the ribosomes; by comparison to polyribosomes, 74S ribosomes are deficient at least fivefold in receipt of new messenger RNA molecules.

Characterization of a temperature-sensitive, hexon transport mutant of type 5 adenovirus

Infection of KB cells at 39.5 degrees C with H5ts147, a temperature-sensitive (ts) mutant of type 5 adenovirus, resulted in the cytoplasmic accumulation of hexon antigen; all other virion proteins measured, however, were normally transported into the nucleus. Immunofluorescence techniques were used to study the intracellular location of viral proteins. Genetic studies revealed that H5ts147 was the single member of a nonoverlapping complementation group and occupied a unique locus on the adenovirus genetic map, distinct from mutants that failed to produce immunologically reactive hexons at 39.5 degrees C ("hexon-minus" mutants). Sedimentation studies of extracts of H5ts147-infected cells cultured and labeled at 39.5 degrees C revealed the production of 12S hexon capsomers (the native, trimeric structures), which were immunoprecipitable to the same extent as hexons synthesized in wild type (WT)-infected cells. In contrast, only 3.4S polypeptide chains were found in extracts of cells infected with the class of mutants unable to produce immunologically reactive hexon protein at 39.5 degrees C. Hexons synthesized in H5ts147-infected cells at 39.5 degrees C were capable of being assembled into virions, to the same extent as hexons synthesized in WT-infected cells, when the temperature was shifted down to the permissive temperature, 32 degrees C. Infectious virus production was initiated within 2 to 6 h after shift-down to 32 degrees C; de novo protein synthesis was required to allow this increase in viral titer. If ts147-infected cells were shifted up to 39.5 degrees C late in the viral multiplication cycle, viral production was arrested within 1 to 2 h. The kinetics of shutoff was similar to that of a WT-infected culture treated with cycloheximide at the time of shift-up. The P-VI nonvirion polypeptide, the precursor to virion protein VI, was unstable at 39.5 degrees C, whereas the hexon polypeptide was not degraded during the chase. It appears that there is a structural requirement for the transport of hexons into the nucleus more stringent than the acquisition of immunological reactivity and folding into the 12S form.

Localization of adenovirus 2 messenger RNA's to segments of the viral genome defined by endonuclease R-R1

Adenovirus 2 mRNAs synthesized in productive infection were assigned to specific regions of the genome by hybridization to unique fragments of viral DNA. Radioactive viral RNA synthesized early or late in infection was first fractionated by polyacrylamide gel electrophoresis. Eluted RNAs were then tested for complementary hybrid formation with each of the six fragments of adenovirus 2 DNA generated by cleavage with endonuclease R.R1. Early RNA species migrating as 13S, 19S, and 20S RNAs were identified as transcription products of fragments A, B, and D, respectively. In addition to the 13S RNA transcribed from A fragment DNA, 13S RNA also hybridized to the D and E fragment DNAs; 11S RNA annealed to both A and B fragments. The RNA that hybridized to fragment C DNA was heterogeneous in size. Viral RNA synthesized late in infection included 27S, 24S, 19S, and 11S size classes, all of which annealed to A fragment DNA. Additional RNA migrating as 24S hybridized to E and C fragment DNA, and 23S RNA annealed to F fragment DNA. The results of the hybridizations of size fractionated RNAs with viral DNA fragments enabled formation of a partial map of viral mRNAs with respect to the adenovirus 2 genome. Some of the viral RNAs may represent transcripts which overlap R1 cleavage sites, because in at least three instances hybridization revealed viral RNAs which have the same electrophoretic mobility and anneal to fragments that are contiguous on the genome.

Transcription of the adenovirus genome by an -amanitine-sensitive ribonucleic acid polymerase in HeLa cells

The properties of the ribonucleic acid (RNA) polymerase activity which transcribes the major portion of the adenovirus genome were studied. Nuclei were prepared from infected cells and incubated in vitro. Virus-specific RNA was determined by hybridization to adenovirus deoxyribonucleic acid (DNA). Adenovirus DNA is transcribed principally by an activity which resembles closely polymerase II of the host cell. This activity is inhibited by alpha-amanitine and stimulated by (NH(4))(2)SO(4). Its product is high-molecular-weight heterogeneous RNA. The polymerase activity measured early in infection (3 to 5 hr) resembles that found late in infection (16 to 18 hr).

Synthesis of virus-specific ribonucleic acid in KB cells infected with type 2 adenovirus

By using the technique of deoxyribonucleic acid (DNA)-ribonucleic acid (RNA) hybridization, virus-specific RNA (cRNA) was detected 6 hr after infection in preparations of total RNA from cells infected with type 2 adenovirus in the presence of 2 mum 5-fluorodeoxyuridine. In the absence of 5-fluorodeoxyuridine, there was a continuous increase in the incorporation of (3)H-uridine into viral cRNA until 20 hr after infection, at which time approximately 40% of the (3)H-uridine entering RNA was found in virus-specific RNA. When RNA was prepared from polyribosome fractions obtained from cytoplasmic extracts of infected cells, virus-directed transcription was detected at 3 hr after infection (i.e., 3 to 4 hr before the initiation of viral DNA synthesis). Viral cRNA species synthesized at different times after infection were compared by the technique of DNA-RNA hybridization-inhibition ("presaturation" hybridization-competition). Three hybridization-inhibition techniques were compared. The techniques differed in the manner in which the DNA-RNA complex was isolated after the first hybridization reaction. Depending on the procedure employed, various degrees of inhibition were measured. The variation could be essentially eliminated if prior to hybridization the inhibitory RNA species were alkali-degraded to a uniform size of about 4S. Undegraded RNA could be used if the DNA-RNA complex was isolated by using a procedure involving rigorous washing (preferably including ribonuclease treatment) before the second hybridization with labeled RNA. When a rigorous hybridization-inhibition procedure was used, three classes of virus-specific RNA species could be distinguished: (i) early RNA class I whose synthesis began prior to viral DNA replication and stopped at some time after the initiation of viral DNA replication-it comprised about 70% of the early RNA species and was apparently degraded by 18 hr after infection; (ii) early RNA class II whose synthesis began prior to viral DNA replication and apparently continued at an enhanced rate late in infection; and (iii) late RNA whose synthesis began after the initiation of viral DNA synthesis.

Transient stimulation of deoxyribonucleic acid-dependent ribonucleic acid polymerase and histone acetylation in human embryonic kidney cultures infected with adenovirus 2 or 12: apparent induction of host ribonucleic acid synthesis

The synthesis of cell-specific ribonucleic acid (RNA) appeared to be stimulated in human embryonic kidney (HEK) cultures infected with adenovirus 2 or 12. Deoxyribonucleic acid (DNA)-RNA hybridization experiments revealed that by 44 to 70 hr after infection with either virus, the relative amount of pulse-labeled RNA capable of hybridizing with HEK cell DNA increased considerably; such RNA was detected in both nuclear and cytoplasmic fractions. The main increase in apparent host RNA synthesis was preceded by (i) a relatively early transient stimulation of the DNA-dependent RNA polymerase activity in isolated nuclei, and (ii) a small but consistently observed increase in the rate of acetylation of lysine-rich and arginine-rich histone fractions. The Mn(2+)-(NH(4))(2)SO(4) and Mg(2+)-activated RNA polymerase reactions measured in nuclei isolated from cells infected with adenovirus 2 or 12 were stimulated at about the same time; a rapid loss of polymerase activity followed. The augmentation of the two RNA polymerase reactions found in adenovirus 12-infected cells was independent of protein synthesis. After the initial increase, the acetylation rate of histones of cells infected with adenovirus 2 or 12 declined, until late in infection it was approximately 40 to 70% of the control cell rate.

Retention or viral antigen in the cytoplasm of cells infected with temperature-sensitive mutants of an avian adenovirus

Immunofluorescent studies were made on chicken kidney cell cultures infected with various temperature-sensitive (ts) mutants of an avian adenovirus, chicken embryo lethal orphan (CELO), which grow well at the nonrestrictive temperature of 31 degrees , but fail to grow at the restrictive temperature of 40 degrees . At 40 degrees some mutants (ts 5, 8, and 10) accumulated viral antigen in the cytoplasm, but scarcely at all in the nucleus. However, at 31 degrees they accumulated the antigen in the nucleus like the wild-type strain at either 31 degrees or 40 degrees . These mutants seemed to complement each other in nuclear accumulation of antigen at 40 degrees . In cells infected with ts 8, the antigen remaining in the cytoplasm during incubation at 40 degrees was partially transferred to the nucleus even in the presence of an inhibitor of protein synthesis when the temperature was lowered to 31 degrees . The results suggest that viral antigen produced in the cytoplasm is transported to the nucleus and that these ts mutants are defective in this process at 40 degrees .There are apparently two other types of ts mutant: one type (ts 3, 7, and 12), like the wild-type strain, showing nuclear accumulation of antigen at 40 degrees and the other (ts 6, 11, and 17) showing no, or only slight, formation of the antigen at 40 degrees .

Cytoplasmic synthesis of type 5 adenovirus capsid proteins

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Biochemical studies on adenovirus multiplication. 13. Synthesis of virus-specific ribonucleic acid during infection with human adenovirus type 12

The transcription of virus-specific ribonucleic acid (RNA) was studied in KB cells infected with adenovirus type 12 (strain Huie). Viral deoxyribonucleic acid (DNA) synthesis began at 12 to 15 hr after infection, and virus maturation occurred between 20 and 50 hr after infection. The rate of incorporation of (3)H-uridine into RNA per infected cell was stimulated, reaching a maximum of 1.6 times that of uninfected cells at 20 hr after infection. "Early" viral messenger ribonucleic acid (mRNA) constituted 0.1% of RNA synthesized at 11 hr, and "late" viral mRNA constituted 50% of RNA synthesized at 45 hr after infection, as determined by hybridization of viral DNA with labeled RNA from infected cells pulse labeled with (3)H-uridine. The species of virus-specific RNA synthesized at 22 hr after infection (when virus maturation has just begun) and at 45 hr (when virus maturation is nearly complete) were studied further: (i) 22- and 45-hr RNA had the same average guanine plus cytosine content, 47%, (ii) 22- and 45-hr RNA contained mostly the same viral nucleotide sequences, (iii) 45-hr RNA had a five times higher concentration of virus-specific RNA molecules than did 22-hr RNA, and (iv) 22- and 45-hr RNA contained virus-specific nucleotide sequences transcribed from all, or nearly all, of the viral genome.

The mechanism of internuclear transmission of SV40-induced complement fixation antigen in heterokaryocytes

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Electron microscopy of adenovirus 12 replication. 1. Fine structural changes in the nucleus of infected KB cells

The ultrastructure of KB cells infected with oncogenic adenovirus 12 was studied at various intervals from 4 to 72 hr after viral inoculation. At 12 hr after infection, the nucleus and the nucleolus became hypertrophic. At 16 hr, bundles of fibers digestable by proteolytic enzymes were seen in the nucleus; they are considered as the early viral antigens identified immunologically by others. Between 24 and 26 hr, four types of nuclear inclusions appeared. Their sequence of appearance and fine structure are described. On the basis of their sensitivity to proteolytic digestion in thin sections, and the results of immunoferritin studies made by others, some of these inclusions are believed to represent viral structural antigens. Throughout the cycle of viral replication, the nucleolus displayed prominent and constant changes in the form of focal condensations and loosening of the nucleolonema, followed by atrophy and fragmentation. It is suggested that the early nucleolar changes reflect an active participation of the nucleolus in the synthesis of adenovirus 12. A hitherto unknown striated structure with definite periodicity, which is easily digested by proteolytic enzymes, was found in the nuclei during the late stages of adenovirus 12 replication.