In an unknown order of events, RNA polymerase II initiates transcription and the Integrator complex (Baillat et al. 2005) and Little Elongation Complex (LEC, Hu et al. 2013) are recruited to phosphorylated RNA polymerase II (Egloff et al. 2010). The Integrator complex interacts with RPAP2, which binds phosphoserine-7 of the C-terminal domain (CTD) of RNA polymerase II and is required for recruitment of Integrator (Egloff et al. 2007, Egloff et al. 2012). RPAP2 interacts with the putative scaffold proteins RPRD1A and RPRD1B at the CTD (Ni et al. 2011, Ni et al. 2014) and DSIF is required for recruitment of Integrator (Skaar et al. 2015). The Integrator complex does not seem to play a significant role in subsequent elongation of the pre-snRNA transcript but is critical for processing of the 3' end of the pre-snRNA.