Genome-wide polyubiquitylation activities on meiotic chromosomes are reduced in UBR2−/− spermatocytes.
Surface-spread meiotic chromosomes were coimmunostained with FK1 antibody (red) which specifically recognizes polyubiquitin conjugates and an antibody to SCP3 (green), a component of the synaptonemal complex. (A) Zygotene. (B) Early pachytene. (C) Mid-pachytene. Arrowhead indicates the sex chromosome. Note that polyubiquitin signals are virtually nondetectible in UBR2−/− chromosomes. Scale bar: 10 µm.