Dosage compensation in Drosophila is mediated by the MSL complex, which 
increases male X-linked gene expression approximately 2-fold. The MSL complex 
preferentially binds the bodies of active genes on the male X, depositing 
H4K16ac with a 3' bias. Two models have been proposed for the influence of the 
MSL complex on transcription: one based on promoter recruitment of RNA 
polymerase II (Pol II), and a second featuring enhanced transcriptional 
elongation. Here, we utilize nascent RNA sequencing to document dosage 
compensation during transcriptional elongation. We also compare X and autosomes 
from published data on paused and elongating polymerase in order to assess the 
role of Pol II recruitment. Our results support a model for differentially 
regulated elongation, starting with release from 5' pausing and increasing 
through X-linked gene bodies. Our results highlight facilitated transcriptional 
elongation as a key mechanism for the coordinated regulation of a diverse set of 
genes.