Fig. 4. Subcellular and chromosomal distribution of the CAK and the core complexes of TFIIH in third-instar larvae salivary gland and polytene chromosomes. (a) Immunolocalization of CDK7 shown in red and DNA staining in green. (b) Immunolocalization of XPD (red) and DNA (green) in third-instar salivary glands. (c) Co-immunostaining of CDK7 (red) and XPD (green) in polytene chromosomes. Most of the two proteins colocalize in a specific euchromatin banding pattern and the signal is enriched in the puffs. An amplified view of the CDK7/XPD immunolocalization in polythene chromosomes is shown. The arrows indicate sites where CDK7 does not colocalize with XPD in the chromatin. (d) Chromosomal distribution of MAT1 and XPD in polytene chromosomes. The red signal is MAT 1 and the green signal is XPD. The arrows indicate an example of a site where MAT1 is localized without XPD in an amplified image.