Polyribosome distribution of HOTAIRM1 and HOXA1 transcripts in ATRA-induced NB4 cells. (A) Polyribosome distribution among fractions from top to bottom (1-22) along the gradient of increasing sucrose density. (B) Multiplex RT-PCR analysis of HOTAIRM1 transcripts in gradient fractions, compared with the distributions of HOXA1 and α-tubulin (TUBA1B) mRNAs, as indicated.