Phorbol esters modulate the phosphorylation of human T-cell leukemia virus type I Tax.
AUTOR(ES)
Fontes, J D
RESUMO
The Tax protein from human T-cell leukemia virus type I (HTLV-I) is a 40-kDa phosphoprotein capable of activating transcription from its own long terminal repeat (LTR), as well as increasing the transcription of cellular genes. Transcriptional activation of the HTLV-I LTR has been demonstrated via a cyclic-AMP-responsive element within the 21-bp Tax-responsive elements of the LTR. Phorbol esters also upregulate expression via the LTR. Since phosphorylation of Tax may play a role in these processes, we investigated the relative effects of kinase-stimulating agents on 32P incorporation into Tax. Our studies demonstrated that the phorbol ester 4 beta-phorbol-12 beta-myristate-13 alpha-acetate greatly stimulated Tax phosphorylation in a time- and dose-dependent manner. In contrast, 8-bromoadenosine 3'-5'-cyclic monophosphate induced little stimulation of Tax phosphorylation. Tax phosphorylation occurred only on serine residues and was mapped to a single tryptic fragment in both Tax-producing human lymphocytes and mouse fibroblast cells.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=237821Documentos Relacionados
- Mutational analysis of human T-cell leukemia virus type 2 Tax.
- Definition of a minimal activation domain in human T-cell leukemia virus type I Tax.
- Utilization of signal transduction pathway by the human T-cell leukemia virus type I transcriptional activator tax.
- Naturally occurring variants of human T-cell leukemia virus type I Tax protein impair its recognition by cytotoxic T lymphocytes and the transactivation function of Tax.
- Role of Tax protein in human T-cell leukemia virus type-I leukemogenicity
