A Immunoblot analysis of immunoprecipitated Flag-tagged histone H2B using anti-Flag or anti-SUMO antibodies in the indicated mutants, The upper and lower panels show Flag-H2B-SUMO and Flag-H2B-ub, respectively. One, two or three asterisks indicate mono-, di-, and poly-sumoylated histones (upper panel), respectively, and an arrowhead and bullet point represent mono-ubiquitylated H2B, and a non-specific band, respectively. 