RESUMEN
The Apolipoprotein B mRNA-editing catalytic polypeptide-like 3 (APOBEC3) genes are able to inhibit the replication of a wide range of exogenous retroviruses, as well as endogenous retroviruses and retrotransposons. Three APOBEC3 genes, named APOBEC3Z1, APOBEC3Z2 and APOBEC3Z3, have been described in sheep. In this work the three genes have been screened in order to identify polymorphisms. No polymorphism was detected for the A3Z2 and A3Z3 genes but 16 SNPs and a 3-bp deletion were found in the A3Z1 gene. A thermoestability prediction analysis was applied to the detected amino acidic SNPs by three different programs. This analysis revealed a number of polymorphisms that could affect the protein stability. The SNPs of the 3'UTR were tested to detect alterations on the predicted microRNA target sites. Two new microRNA target sites were discovered for one of the alleles. Two SNPs were selected for association studies in relation with the retroviral disease Visna/Maedi in Latxa and Assaf sheep breeds. Although association analyses resulted unconclusive, probably due to the unsuitability of the SNP allele frequency distribution of the selected polymorphisms in the analyzed breeds, these genes remain good candidates for association studies.