Sequencing and comparative analysis of hexon gene of fowl adenovirus 4 of Indian origin

The sequencing of the recombinant plasmid containing 2916 bp hexon gene insert of fowl adeno virus 4 (FAV4) of Indian origin revealed the complete nucleotide sequence of the FAV4 hexon gene. The sequence analysis revealed an open reading frame of 2814 bp coding for a 937 amino acids long polypeptide with a molecular mass of 106.04 kDa. This sequence was larger than the hexon coding regions of FAV10, HAV40, HAV41, MAV1 and BAV3, while it was smaller than the hexon in HAV2 and HAV5. The Kozak sequence was found at nucleotide position 78, which was similar in FAV10 hexon gene. The codon bias revealed a strong preference for C and to a lesser extent G in the third base position. The splice acceptor sequence in FAV4Ind was located 12 bp upstream of the hexon initiation site of the translation codon, which indicated that FAV4 hexon could be a late gene product. A high degree of amino acid variation (9.6%) was observed between FAV4Ind and FAV10, as compared to the 1.5% variation between FAV4Ind and FAV4KR95. The L1 loop of the hexon gene showed the maximum sequence variation among FAV serotypes, thus it could be used for designing serotype specific PCR primers. The 11 unique amino acid substitutions in FAV4Ind hexon could play a significant role in determining its type specificity.