RNA binding domain of HDV antigen is homologous to the HMG box of SRY

The delta antigen of hepatitis delta virus exhibits sequence specific bindi ng to its own RNA and is essential for viral replication. Using statistical methods we have detected significant similarity between the RNA-binding do main of the hepatitis delta antigen and the HMG box of SRY. Our analysis su ggests that the RNA-binding domain of HDV antigen evolved from the DNA-bind ing domain of the HMG box. SRY, or a related protein, is a probable cellula r cognate of HDV.