FISH investigation on the MYB gene and structure of MYB-GATA1. (A) Red signal corresponding to RP11-104D9 and spanning the 5′ part of MYB is delocalized on der(X). Localization of BACs on the chromosome 6 is schematized on the left. Normal chromosome 6 (chr.) and derivative chromosomes (der) are indicated. (B) Nucleotide sequence of the fusion mRNA (C) Schematic representation of MYB, GATA1 and MYB-GATA1 proteins. MYB is composed of R1, R2, and R3, which are 3 imperfect 52-residue repeats that encompass the DNA-binding domain (DBD) of MYB. TAD is the transactivation domain of MYB containing a conserved acidic domain and NRD is the negative regulatory domain including a leucine zipper motif (LZ). GATA1 is composed of an activation domain (AD) and 2 zinc finger domains. MYB-GATA1 keeps both the DBD and TAD of MYB and the c-terminal zinc finger domain of GATA1. The breakpoint at the amino acid level is indicated by the black arrow. Of note, the TAD of MYB has lost 9aa (241 to 316) compared with the reference¹¹  (241 to 345) but this portion retains the minimal TAD¹²  (290 to 315).