We have characterized cDNA clones representing mouse
CREB (cyclic AMP responsive element binding protein)
mRNA isoforms. These include CREBA and CREBa, of
which the rat and human homologues have been
previously identified. Both encode proteins with CREbinding
activity and identical transactivation potential.
The additional CREB mRNA isoforms potentially encode
CREB related proteins. From the structural organization
of the mouse CREB gene we conclude that the multiple
transcripts are generated by alternative splicing. Furthermore
we show that specific CREB mRNA isoforms are
expressed at a high level in the adult testis. Expression
of these isoforms is induced after commencement of
spermatogenesis. In situ hybridization suggests that this
expression occurs predominantly in the primary spermatocytes.
Comparison of the CREB gene with the recently
isolated CREM (cAMP responsive element modulator)
cDNAs illustrates that the two genes have arisen by gene
duplication and have diverged to encode transcriptional
activators and repressors of the cAMP signal transduction
pathway
