Here we report the codon bias and the mRNA secondary structural features of the hemagglutinin(HA)cleavage site basic amino acid regions of avian influenza virus H5N1 subtypes.We have developed a dynamic extended folding strategy to predict RNA secondary structure with RNAstructure 4.1 program in an iterative extension process.Statistical analysis of the sequences showed that the HA cleavage site basic amino acids favor the adenine-rich codons,and the corresponding mRNA fragments are mainly in the folding states of single-stranded loops.Our sequential and structural analyses showed that to prevent and control these highly pathogenic viruses,that is,to inhibit the gene expression of avian influenza virus H5N1 subtypes,we should consider the single-stranded loop regions of the HA cleavage site-coding sequences as the targets of RNA interference.
