No abstract

The signal sequence of simian virus 40 (SV40) large T-antigen for translocation into the nucleus is composed of positively charged amino acids Lys-Lys-Lys-Arg-Lys. Rabbit antibodies to a synthetic peptide containing the negatively charged amino acid sequence Asp-Asp-Asp-Glu-Asp were obtained. Indirect immunofluorescence of the antigens recognized by the antibody was punctate at the nuclear rim or the nuclear surface, depending on the plane of focus. The antibody blocked transport of nuclear proteins into the nucleus. The antigens recognized by the antibody were predominantly localized to the nuclear pores.

The total genome sequence of L11A, an attenuated strain of tobacco mosaic virus (TMV), has been determined. This strain is able to multiply in tomato plants without inducing any remarkable symptoms, but to protect them from later infection with virulent TMV strains. When compared with the recently published total genome sequence of TMV L (the virulent ancestral strain of L11A) ten base substitutions were found in the L11A genome. Seven of these occurred in the third letters of in-phase codons and did not influence amino acids. Only three, which were in the common reading frame for both the 130K and 180K proteins, resulted in amino acid changes. Together with the result of the partial sequence of RNA of L11, an intermediate strain in sequential isolation from L to L11A, it is observed that one base at the nucleotide position 1117 is changed from L to L11 and two bases at the positions 2349 and 2754 are changed from L11 to L A11.

No abstract

In vivo uncoating of tobacco mosaic virus (TMV) was studied. As Shaw had reported, initiation of uncoating reaction takes place very efficiently. Coat protein is removed from the virus as a peptide which is precipitable with trichloroacetic acid. Short rod particles with partly exposed RNA are thus formed. Further uncoating to coat protein-free TMV-RNA (28S) seems to take place with very low efficiency which is comparable to that of formation of local lesions on the inoculated leaf. From the data on the intracellular distribution of these products of uncoating reaction, mechanisms and significance of these reactions are discussed.The first process after viral infection is the release of the viral aenome from its protein coat. Little information is available at present about the mechanism of this uncoating process in plant virus infection. With tobacco mosaic virus (TMV) labeled with 1+C in its protein moiety, Shaw [7] had shown that the removal of protein coat from TMV after infection of tobacco leaves begins almost immediately after infection and proceeds until about half the total virus protein had been removed at 5 hours. Results suggest that almost all TMV particles retained by the leaves are partially uncoated. In parallel with this findings, some naked parental RNA was detected after TMV infection by Reddi [6]. Furthermore he isolated RNase sensitive RNA from nucleus fraction of leaves obtained at 2 days after infection. As the nucleotide composition of this RNA resembles that of TMV-RNA, he claimed that it is TMV-RNA. If it is true, the size of this RNA should be 28S. Actually, there has been no report of isolation of a free 28S RNA from leaves shortly after infection.These works suggest that the initiation of uncoating reaction takes place very efficiently. However, it stops soon and the efficiency of completely uncoating to 28S TMV-RNA seems to be low. This may reflects the low efficiency of establishment of TMV infection [8]. Why does uncoating process stop soon after infection? In order to solve this problem, we investigated the details of uncoating process using 32P or 35S labeled TMV . In this paper, we report on the nature of the product of the uncoating reaction.