Schematic representation of the genomic organization of the CDKN2A/ARF-CDKN2B gene cluster on chromosome 9p21.3.CDKN2A and ARF share the same exons 2 and 3 but include different first exons (1α and 1β). The alternative splicing of exon 1α or exon 1β to exons 2 and 3 gives rise to a difference in the reading frames between CDKN2A and ARF, thereby accounting for the absence of any amino acid homology between the proteins encoded by CDKN2A and ARF. The long non-coding RNA ANRIL (antisense non-coding RNA in the INK4 in locus) gene contains 19 exons and is transcribed in the antisense orientation of the CDKN2A/ARF-CDKN2B gene cluster. Black arrows indicate the transcriptional orientation of the genes at 9p21.3. The red arrow indicates the relative position of the SNP rs2151280 within ANRIL intron 3.
Mußotter et al. BMC Medical Genetics 2012 13:98 doi:10.1186/1471-2350-13-98