Drosophila Chromosome 4 Chromatin Structure Figure 5. Lack of HP1a or POF shifts the enrichment pattern of RNA pol II on chromosome 4. A. RNA pol II distribution of expressed genes on chromosome 4, comparing wildtype (WT) to HP1a (red) and POF (blue) mutants. Chromosome 4 genes are compared to genes with similar expression levels randomly chosen from the euchromatin on chromosome arm 3R (N = 58 for both). Note the dramatic loss of RNA pol II enrichment PLOS Genetics | www.plosgenetics.org 8 September 2012 | Volume 8 | Issue 9 | e1002954