module: dmel_cohesin_complexes
title: Mitotic and meiotic cohesin complexes in Drosophila melanogaster
label: Cohesin complexes
module_type: PROTEIN_COMPLEX
description: >-
  Cohesin is a ring-shaped SMC complex that holds sister chromatids together
  from DNA replication until anaphase and also organizes interphase chromatin
  into loops. The ring is built from the SMC1-SMC3 heterodimer, whose ATPase
  heads are bridged by a kleisin subunit, which in turn binds a stromalin (SA)
  subunit. In mitotic cells the kleisin is Rad21, encoded in Drosophila by
  verthandi (vtd), and the SA subunit is SA1; separase cleavage of Rad21 opens
  the ring at anaphase. Drosophila meiosis uses meiosis-specific cohesion
  proteins: C(2)M, a kleisin-family protein required for synaptonemal complex
  formation, and Solo and Sunn, which are required for meiotic centromeric
  cohesion.
summary: >-
  SMC1-SMC3 cohesin rings with a mitotic Rad21/Vtd-SA kleisin module or
  meiosis-specific C(2)M or Solo-Sunn subunits.
concepts:
  - {id: GO:0008278, label: cohesin complex}
cellular_components:
  - {id: GO:0000785, label: chromatin}
parts:
  - id: smc1_smc3
    label: SMC1-SMC3 heterodimer
    role: SMC ATPase ring
    description: SMC1 and SMC3 form the ATPase core shared by all cohesin variants.
    genes: [SMC1, SMC3]
    unit_functions:
      SMC1: {id: GO:0016887, label: ATP hydrolysis activity}
      SMC3: {id: GO:0016887, label: ATP hydrolysis activity}
  - id: kleisin_sa_module
    label: Kleisin and accessory subunits
    role: ring closure and variant-specific subunits
    variant_sets:
      - id: cohesin_variants
        label: Mitotic or meiotic non-SMC subunits
        selection: ONE_OR_MORE
        variants:
          - id: mitotic_rad21_sa
            label: Mitotic Rad21 (Vtd) and SA1
            genes: [vtd, SA1]
            processes:
              - {id: GO:0007064, label: mitotic sister chromatid cohesion}
          - id: meiotic_c2m_sa
            label: Meiotic C(2)M and SA1
            genes: [c(2)M, SA1]
            complex_term: {id: GO:0030893, label: meiotic cohesin complex}
            processes:
              - {id: GO:0051177, label: meiotic sister chromatid cohesion}
          - id: meiotic_solo_sunn
            label: Meiotic Solo and Sunn
            genes: [solo, sunn]
            complex_term: {id: GO:0030893, label: meiotic cohesin complex}
            processes:
              - {id: GO:0051177, label: meiotic sister chromatid cohesion}
notes: >-
  The three FlyBase groups (COHSN, COHSN-SOLO-SUNN, COHSN-C2M-SA) share SMC1
  and SMC3, which are modelled once as the core part; the variant-specific
  subunits form a variant set. The meiotic complex term is placed on the
  meiotic variant nodes even though each node lists only its non-SMC
  subunits. Cohesin loaders (Nipped-B, Mau-2), Pds5, Wapl, separase and
  shugoshin (MEI-S332) are regulators outside the module. The SMC subunits are given ATP hydrolysis activity (GO:0016887), which
  they carry in GOA (ISS, NAS, IEA); their ATPase heads, engaged across the
  heterodimer, drive the complex. GO has a complex-level term for SMC-complex
  DNA entrapment (GO:0061776 ATP-dependent topological DNA co-entrapment
  activity, used by PomBase for the fission yeast complexes), but it is not
  annotated to the Drosophila proteins and is not asserted here.