Identification of Triad1. (A) Northern blot hybridization using subtracted clone 14-5 detecting the ATRA-mediated induction of a 4-Kb transcript in NB4 cells (time of ATRA incubation is given at the top in hours). Rehybridization with a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) probe indicates equal loading. (B) Triad1 5′- and 3′-RACE and RT-PCR fragments as depicted in panel 1C (lane numbers correspond to fragment numbers in panel 1C). Alternative splicing results in the detection of 2 RT-PCR fragments (lane 2). RACE and PCR fragments 1 to 5 were amplified using primer combinations indicated in Table 1. (C) Schematic representation of the 3.9-Kb ATRA-induced Triad1 transcript (see Figure S1 for sequences). Indicated are the 1479 open reading frame (ORF) (open box) and overlapping cDNA and 5′- and 3′-RACE fragments as well as the localization of fragment 14-5 representing the clone identified in the subtractive PCR screen. (D) Schematic representation of Triad1 protein domains. A indicates acidic domain; R1 and R2, RING finger structures; D, DRIL domain; CC, coiled coil domain.