Y RNAs are components of the Ro ribonucleoprotein particle (Ro RNP), in association with Ro60 and La proteins. The Y RNAs and Ro60 and La proteins are well conserved, but the function of the Ro RNP is not known. In humans the RNA component can be one of four small RNAs: hY1, hY3, hY4 and hY5. These small RNAs are predicted to fold into a conserved secondary structure containing three stem structures. The largest of the four, hY1, contains an additional hairpin.