Moreover, multiple proteins that are mutated in the childhood motor neuron disease cause Spinal Muscular Atrophy (SMA) associate with the RNAP II machinery, including SMN1, EXOSC822, HSPB123,24 and two components (ASCC1 and TRIP4)25,26 of the ASC-1 transcriptional co-activator (BC et al., submitted). Here, SMN1 is linked to proximal spinal muscular atrophy.