Other than suppressing type I interferon induction, both alphacoronaviruses and betacoronaviruses can use nsp1 to degrade host mRNA transcripts, resulting in the suppression of host interferon response, although sequence homology between nsp1 proteins of the two genera remains low. A conserved domain is present in nsp1 of alphacoronaviruses and it is responsible for the shut-down of host gene expression. The deletion of 91–95 amino acids in 229E and NL63 nsp1 partially restores host gene expression as shown by luciferase reporter assay [63]. The interferon-modulating activity of nsp1 shows some variations within the genus of Betacoronavirus. Whereas nsp1 proteins encoded by SARS-CoV and bat CoV Rm1 potently suppress the induction of type I interferon, counterparts in bat CoV 133 and bat CoV HKU9-1 are relatively weak interferon suppressors [64]. Again, some degree of conservation in interferon antagonism of nsp1 is seen among different CoVs.