KoRV splice sites. Alignment of env transcript splice donor (A) and acceptor (B) regions from Moloney murine retrovirus (MMLV; database accession [GenBank:AF462057]) and koala retrovirus (KoRV; database accession [GenBank:AF151794]). Positions with identical nucleotides are shaded blue. Intronic sequences are in lower case. Red triangles indicate splice sites supported by experimental evidence.