FIGURE 1.

The mRNA expression pattern in plasma cells favors transcriptional elongation. The mRNA expression in the B cell line (white bars) was compared with that of the plasma cell line (dark gray bars) using dT priming for cDNA synthesis followed by quantitative PCR. Expression of hypoxanthine-guanine phosphoribosyltransferase (HPRT) was set as 1 in each cell type, and the expression relative to hypoxanthine-guanine phosphoribosyltransferase was plotted on the x axis. Note the differences in scales between the groups of mRNA. A, contains mRNAs for the eleven-nineteen lysine-rich leukemia gene 1 or 2 or its associated factors eaf1 and eaf2. ELL2 shows the highest level of induction in plasma cells among this and all groups. B, pTEFb (cdk9 and cyclin T) and associated factors. The highly abundant 7SK RNA was primed by random oligonucleotides for the RT reaction and compared with an hypoxanthine-guanine phosphoribosyltransferase random-primed reaction; the amount of 7SK was divided by 1,000 to plot it on the same scale as the other pTEFb factors. Many of these factors are significantly increased in plasma cells. C, components of the super elongation complexes recently described (see “Results”). D, the mRNA abundance of the histone methylases (MLL, Dot1L, and Nsd1), cyclin C (CCNC), and its associated cdk8 and the polyadenylation cleavage factor CstF-64 (pA cstF2). Significant differences in plasma cells versus B cells were determined in the Bonferroni post test following two-way analysis of variance as indicated with *, p ≤ 0.05, **, p ≤ 0.01, ***, p ≤ 0.001, ****, p ≤ 0.0001; the error bars represent S.E. in this and all subsequent graphs derived from at least three different biological replicates.