Fig. 1

Isolation of nucleic acid-associated proteins. Formaldehyde was introduced into bacterial cultures to stabilize protein-nucleic acid interactions through crosslinking. Bacterial cells were lysed and protein-DNA complexes fragmented prior to immunoprecipitation using an anti-RNA polymerase antibody immobilized on protein G coated magnetic beads. Immunoprecipitated proteins were digested of magnetic beads using trypsin and mass spectrometry analysis was performed to identify nucleic acid-associated proteins