Confirmation of internally deleted variant B29 mRNA in B-CLL 19 cells. Total cellular RNA samples from patient CLL 19 (10 μg each) were independently reacted with an antisense riboprobe for either wild-type B29 mRNA (ie, 630-nt long) or for the internally deleted variant B29 mRNA cloned from this patient (ie, 588-nt long) and analyzed in RPA. Lanes (left to right) 1 and 4, molecular weight markers; lane 2, control of both riboprobes digested with tRNA; lane 3, undigested wild-type (630 nt) and variant (588 nt) B29 riboprobes; lane 5, protected RPA product obtained with wild-type (630 nt) B29 riboprobe; lane 6, protected RPA products obtained with internally deleted CLL 19 variant (588 nt) B29 riboprobe. β-Actin riboprobe digestion products are shown in lanes 5 and 6 to confirm equivalent RNA inputs.