Characterisation and developmental regulation of the Xenopus laevis CCAAT-enhancer binding protein beta gene

We report here the cloning, characterisation and developmental expression p rofile of the Xenopus laevis CCAAT-enhancer binding protein beta (xC/EBP be ta) gene. The protein synthesised from the xC/EBP beta gene interacts speci fically with a C/EBP-recognition sequence and acts as a transcriptional act ivator. Several conserved regions are present in the xC/EBP beta sequence, including the basic region, leucine zipper, activation domains, three in-fr ame AUG codons, and a consensus site for mitogen activated protein kinase. The corresponding mRNA is present at high levels in the kidney, liver, lung , muscle and adipose tissue, and at low levels in the ovary, brain and hear t. Although the xC/EBP beta mRNA and protein are present throughout embryog enesis, there is a biphasic increase in their expression levels during deve lopment. Whole-mount in situ hybridisation shows a restricted spatial expre ssion profile of the xC/EBP beta gene during early embryogenesis, with tran scripts present around the blastopore lip and in the endodermal cells at th e mid-gastrula stage, and, the whole dorsal side at the neurula and early t ailbud stage. The expression domain becomes almost ubiquitous during later embryonic development, and includes the brain, spinal cord, somites and reg ions that give rise to the liver and the heart. (C) 1998 Elsevier Science I reland Ltd. All rights reserved.