The majority of cDNA clones with strong positive signals for the interferon-induction-specific sequences resemble mitochondrial ribosomal RNA genes.

A complementary DNA library prepared from the 12S polyadenylated RNAs extracted from interferon-induced KG-1 cells, a human myeloblast cell line, was screened for the presence of induction-specific sequences. Clones that exhibited strong positive signals were separated by hybridization criteria into nine classes. Clones from classes I through IV consisted of about 78% of the total and unexpectedly were found to resemble human mitochondrial ribosomal RNA genes.