CLONING AND EXPRESSION OF 2 PROOPIOMELANOCORTIN MESSENGER-RNAS IN THECOMMON CARP (CYPRINUS-CARPIO L.)

Proopiomelanocortin (POMC) is the precursor for a number of biological ly active peptide such as adrenocorticotropic hormone (ACTH), alpha-me lanocyte-stimulating hormone (alpha-MSH) and beta-endorphin. It is wel l known that these peptides are involved in the stress response in fis h as well as in mammals. We have cloned two different carp POMC cDNAs called, POMC-I and POMC-II. The nucleotide sequences of 955 bp for POM C-I and 959 bp for POMC-II share 93.5% identity in their cDNAs, and th e deduced amino acid sequences (both 222 amino acids) are 91.4% identi cal. In the ACTH and beta-MSH domain, two amino acid substitutions are found, whereas alpha-MSH and beta-endorphin are identical. For beta-M SH, the serine replacement (in POMC-I) by a glycine (in POMC-II) resul ts in a putative amidation site Pro-X-Gly for POMC-II. We used RT-PCR to show that both POMC mRNAs are expressed in the hypophysis, hypothal amus and other parts of the brain of a single fish. Furthermore, in a phylogenetic tree based on POMC sequences the divergence of carp POMC- I and -II from tetraploid animals (salmon, trout and xenopus) is demon strated. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.