Ž . Biochimica et Biophysica Acta 1352 1997 249–252 Short-sequence paper Cloning and sequence analysis of human calcyphosine complementary DNA 1 Hakim El Housni, Adrian Radulescu, Raymond Lecocq, Jacques E. Dumont, Daniel Christophe ) IRIBHN, UniÕersite Libre de Bruxelles, Faculte de Medecine, 808 route de Lennik, Bat. C, 1070 Brussels, Belgium ´ ´ ´ ˆ Received 4 April 1997; accepted 15 April 1997 Abstract Calcyphosine, initially identified as thyroid protein p24, is a calcium-binding protein containing four EF-hand domains. It was first cloned and characterized in the dog and corresponds to R2D5 antigen in rabbit. Using the canine calcyphosine cDNA sequence as a probe, we have isolated its human counterpart from a thyroid cDNA library. The two sequences display a high degree of conservation, both at nucleotide and deduced amino acid levels. Sequence comparison with other proteins showed that the closest homologue of calcyphosine is the crustacean CCBP-23 protein. Northern blot analysis revealed that calcyphosine messenger RNA is much less abundant in human than in canine thyrocytes. Western blot experiments indicated that the amount of protein is also dramatically reduced in man compared to dog. q 1997 Elsevier Science B.V. Keywords: Calcyphosine; Calcium; cAMP; Thyroid Calcyphosine was cloned from a dog thyroid cDNA wx library by Lefort et al. 1 . It is a calcium-binding protein containing four EF-hand domains whose syn- thesis and phosphorylation is up-regulated by cAMP agonists in thyrocytes. Based on sequence similari- ties, calcyphosine is closely related to calmodulin w x 2,3 . It distinguishes itself by the presence of two insertions, of 2 and 17 amino acids respectively, in the fourth EF-hand domain canonical motif and by a restricted tissue distribution. Cloning of the rabbit R2D5 antigen from olfactory epithelium revealed that ) Corresponding author. Fax: q32 2 555 4655. E-mail: dchristo@ulb.ac.be 1 Accession number: X97966. it constitutes the homologue of calcyphosine in this wx species 4 . R2D5 antigen presents 86% identity with dog calcyphosine and has been reported to be phos- phorylated by protein kinase A and Ca 2q rcalmodu- Ž . lin-dependent protein kinase II CaM kinase II in vitro. The calcium-binding property and phosphoryla- tion characteristics of calcyphosine potentially allow it to integrate signals originating from both calcium and cAMP cascades, which could constitute a privi- leged point of cross-signalling between these two regulatory pathways in selected cell types. However, experimental evidence supporting this view is still lacking. The presence of the calcyphosine gene in the wx human genome has been demonstrated 5 . It was localized to the p13.3 region of chromosome 19 by in situ hybridization using a partial human genomic 0167-4781r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved. Ž . PII S0167-4781 97 00073-0