(A) Northern blot analysis of rat iap mRNA expression in adult rat tissues. A rat multiple tissue northern blot (Clontech) containing 2 μg/lane poly(A)+ RNA per lane was probed sequentially with [32P] dCTP (Amersham) labeled, random primed (Amersham Rediprime) DNA probes derived from the coding regions of rat iap-1, iap-2, iap-3, and β-actin (control). Blots were hybridized overnight in 5 × SSPE/10 × Denhardt's solution/100 μg/ml salmon sperm DNA/ 50% formamide/ 2% SDS and then washed with 0.2 × SSC/ 0.1% SDS at 50°C. The position and sizes of the markers are indicated on the left. The tissues represented on the blot are as follows: (1) heart, (2) brain, (3) spleen, (4) lung, (5) liver, (6) skeletal muscle, (7) kidney, and (8) testis. (B) Northern blot analysis of the expression of iap-2 in testes. A rat multiple tissue Northern blot (Clontech; same as in (A)) was hybridized sequentially with [32P] dCTP labeled DNA probes specific to iap-2 coding region, BIR domain and the RING zing finger. The blots were processed as in (A). The position of testis-specific transcript is indicated by an asterisk (*).