Propensity for HBZ-SP1 isoform of HTLV-I to inhibit c-Jun activity correlates with sequestration of c-Jun into nuclear bodies rather than inhibition of its DNA-binding activity.
HTLV-I bZIP factor (HBZ) contains a C-terminal zipper domain involved in its interaction with c-Jun. This interaction leads to a reduction of c-Jun DNA-binding activity and prevents the protein from activating transcription of AP-1-dependent promoters. However, it remained unclear whether the negative effect of HBZ-SP1 was due to its weak DNA-binding activity or to its capacity to target cellular factors to transcriptionally-inactive nuclear bodies. To answer this question, we produced a mutant in which specific residues present in the modulatory and DNA-binding domain of HBZ-SP1 were substituted for the corresponding c-Fos amino acids to improve the DNA-binding activity of the c-Jun/HBZ-SP1 heterodimer. The stability of the mutant, its interaction with c-Jun, DNA-binding activity of the resulting heterodimer, and its effect on the c-Jun activity were tested. In conclusion, we demonstrate that the repression of c-Jun activity in vivo is mainly due to the HBZ-SP1-mediated sequestration of c-Jun to the HBZ-NBs.
Clerc
Isabelle
I
Université Montpellier 1, Centre d'études d'agents Pathogènes et Biotechnologies pour la Santé (CPBS), France; CNRS, UM5236, CPBS, F-34965 Montpellier, France; Université Montpellier 2, CPBS, F-34095 Montpellier, France.
Hivin
Patrick
P
Rubbo
Pierre-Alain
PA
Lemasson
Isabelle
I
Barbeau
Benoit
B
Mesnard
Jean-Michel
JM
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D019281:Dimerization; D015967:Gene Expression Regulation, Viral; D015368:Human T-lymphotropic virus 1 / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018613:Microscopy, Confocal / Q000379:methods; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012191:Retroviridae Proteins; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
D050976:Basic-Leucine Zipper Transcription Factors; C479751:HBZ protein, human T-cell leukemia virus type I; D020033:Protein Isoforms; D012191:Retroviridae Proteins; D014764:Viral Proteins; D004247:DNA; D048031:JNK Mitogen-Activated Protein Kinases