Unusual nucleotide content of Rubella virus genome as a consequence of biased RNA-editing: comparison with Alphaviruses.

The usage of cytosine in third codon positions of 22 complete Rubella virus genomes (52.4%) is significantly higher than the usage of guanine (28.9%), adenine (6.9%) and uracil (11.8%). The percentage of U ↔ C transitions (55%) between 22 Rubella virus genomes is two times higher than the percentage of A ↔ G transitions (23%). Predicted microRNA from ORF1 of Rubella virus may target human APOBEC1 mRNA, blocking APOBEC1-editing of viral RNA-minus and RNA-plus strands (preventing G → A and C → U transitions, respectively), while their ADAR-editing (causing U → C and A → G transitions, respectively) occurs frequently.