URF’s (URFA6L) are 207-nucleotide (nt) reading frames

overlapping out of phase the NH2-terminal portion of the adenosinetriphosphatase

(ATPase) subunit 6 gene. The smallest URF’s has been identified as the animal equivalent of the recently

discovered yeast H+-ATPase subunit 8 gene. In contrast, the functional significance of the other URF’s are elusive.