Regulation of microtubule assembly and stability by the transactivator of transcription protein of Jembrana disease virus.

Microtubules are cytoskeletal polymers consisting of tubulin subunits that take part in diverse cell activities. Many viruses hijack cellular motor proteins to move on microtubules toward the cell interior during the entry process and toward the plasma membrane during the egress period. In addition, viruses often remodel microtubules to facilitate the generation of infectious progeny. In this study, we found that the transactivator of transcription protein of Jembrana disease virus (Jtat) bound tubulin and microtubules both in cells and in the purified system. Microtubule co-sedimentation and co-localization assays revealed a robust interaction of Jtat with microtubules. Tubulin turbidity assay further showed that Jtat promoted tubulin polymerization in vitro in a concentration-dependent manner. Moreover, Jtat promoted the partitioning of cellular tubulin toward the polymeric form, increased the level of tubulin acetylation, and significantly enhanced the cold stability of cellular microtubules. In addition, Jtat-mediated disruption of microtubule dynamics induced the release of Bim from microtubules, leading to profound apoptosis. These results not only identify Jtat as an important viral regulator of microtubule dynamics but also indicate that Jtat-induced apoptosis might contribute to Jembrana disease pathogenesis.

Unique epitope of bovine immunodeficiency virus gag protein spans the cleavage site between p16(MA) and p2L.

Bovine immunodeficiency virus (BIV) and Jembrana disease virus (JDV) are closely related bovine lentiviruses that are difficult to distinguish by presently available diagnostic methods. Recently, in our laboratory, a monoclonal antibody (MAb; MAb 10H1) against the BIV Gag protein identified a differential epitope, located at the 6.4-kDa N terminus of a 29-kDa Gag capsid protein, which was absent in JDV. To define the essential amino acids of the epitope, a series of primers within the 163 bp of DNA corresponding to the 6.4-kDa protein were designed. The full-length 163-bp DNA fragment and the smaller DNA fragments with deletions were amplified by PCR and then cloned into pQE32 vectors for protein expression studies. The expressed proteins were analyzed with MAb 10H1 by Western blotting. The differential epitope has been narrowed to a 26-amino-acid region (R121 to R146), which includes 6 residues of p16(MA) (where MA represents the matrix protein) and 20 residues of p2L. A synthetic peptide corresponding to the putative 26-amino-acid epitope blocked MAb 10H1 binding to the expressed peptide. These experiments revealed that the epitope spans the cleavage site between p16(MA) and p2L and presumably will be valuable in distinguishing the two viruses.

Nucleotide sequence analysis of Jembrana disease virus: a bovine lentivirus associated with an acute disease syndrome.

The complete nucleotide sequence of the RNA genome of Jembrana disease virus (JDV), a lentivirus that causes an acute disease syndrome in Bali cattle (Bos javanicus), is reported. In addition to the gag, pol and env genes and flanking long terminal repeats (LTRs) that characterize all retroviruses, a number of accessory genes represented by small multiply spliced ORFs in the central and 3'-terminal regions of the genome, including tat and rev that are typical of lentiviruses, were identified. The genome of JDV was 7732 bp in length, 750 bp smaller than the genome of bovine immunodeficiency virus (BIV) strain BIV127. A striking feature of the genome was the many deletions relative to BIV127, the largest of which were 471 bp from the env gene and 157 bp from the U3 (promoter) region in the LTR. There were also several insertions of up to 33 bp in the JDV genome relative to BIV127 found in the env gene and small ORFs that overlap env. Other significant genomic differences between JDV and BIV127 included changes to cis-acting sequences throughout the genome such as promoter and enhancer sequences in the LTR, the trans-activation response region, splice sites and frameshift sequences; alterations to the gag precursor protein cleavage sites and thus the processed products; loss of the vpw and vpy ORFs; and amino acid changes in all coding regions. The significance of these changes is discussed in relation to the differences in pathogenicity between JDV and BIV.