The highly structured (64% GC) covalently closed circular (CCC) RNA (220 nt) of 
the virusoid associated with rice yellow mottle virus codes for a 16-kDa highly 
basic protein using novel modalities for coding, translation, and gene 
expression. This CCC RNA is the smallest among all known viroids and virusoids 
and the only one that codes proteins. Its sequence possesses an internal 
ribosome entry site and is directly translated through two (or three) completely 
overlapping ORFs (shifting to a new reading frame at the end of each round). The 
initiation and termination codons overlap UGAUGA (underline highlights the 
initiation codon AUG within the combined initiation-termination sequence). 
Termination codons can be ignored to obtain larger read-through proteins. This 
circular RNA with no noncoding sequences is a unique natural supercompact 
"nanogenome."