FAMILIES OF ADENYLATE-CYCLASE GENES IN TRYPANOSOMA-BRUCEI

Four genes for adenylate cyclase have been characterized in Trypanosom a brucei. One of them, esag 4 (for expression site associated gene 4) is present in different VSG (variant surface glycoprotein) gene expres sion sites and, thus, is only expressed in the bloodstream form of the parasite. The others, termed gresag 4.1, 4.2 and 4.3 (for genes relat ed to esag 4) are expressed in both bloodstream and procyclic forms. I n addition, we cloned a esag 4-related gene from T. congolense. Here w e characterize the genomic organization of gresag 4.1 and 4.3, While g resag 4.3 is unique, gresag 4.1 exists as a multigenic family of at le ast nine members located on a 3-Mb chromosome. Six of them are cluster ed in a region of 300 kb, three copies being tandemly linked. The dete rmination of the nucleotide sequence of a conserved 1.6 kb PstI fragme nt demonstrated the presence of two separate subgroups in this family. This gene arrangement is present in different isolates of T.b. brucei /rhodesiense/gambiense. Several gresag 4.1 copies are transcribed in b oth bloodstream and procyclic forms.