Engineered leucine zippers show that hemiphosphorylated CREB complexes are transcriptionally active.
The ability of basic/leucine zipper transcription factors to form homo- and heterodimers potentially increases the diversity of signaling pathways that can impinge upon a single genetic element. The capacity of these proteins to dimerize in various combinations complicates the analysis of their functional properties, however. To simplify the functional analysis of CREB dimers, we mutated selected residues within the leucine zipper region to generate proteins that could only heterodimerize. These mutants allowed us to determine whether phosphorylation of both CREB subunits was necessary for transcriptional activation. Our results reveal that hemiphosphorylated CREB dimers are half as active as fully phosphorylated dimers. It is possible, therefore, that the degree of phosphorylation of CREB complexes could modulate the transcriptional responses of specific genes to cAMP.
Loriaux
M M
MM
Vollum Institute, Oregon Health Sciences University, Portland 97201.
Rehfuss
R P
RP
Brennan
R G
RG
Goodman
R H
RH
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015723:Gene Library; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism; D016350:Leucine Zippers / Q000235:genetics; D046911:Macromolecular Substances; D051379:Mice; D008961:Models, Structural; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010957:Plasmids; D015202:Protein Engineering / Q000379:methods; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D013004:Somatostatin / Q000235:genetics; D018243:Teratocarcinoma; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D017362:Cyclic AMP Response Element-Binding Protein; D046911:Macromolecular Substances; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D013004:Somatostatin; D015500:Chloramphenicol O-Acetyltransferase