Crystal structure of the malignant brain tumor (MBT) repeats in Sex Comb on Midleg-like 2 (SCML2)

J Biol Chem. 2003 Nov 21;278(47):46968-73. doi: 10.1074/jbc.M306469200. Epub 2003 Sep 1.


Sex Comb on Midleg (SCM) belongs to the Polycomb group of proteins, which are involved in transcriptional regulation in Drosophila. It is one of the components of Polycomb repressive complex 1, a multiprotein complex of Polycomb group proteins involved in the maintenance of repression and the blocking of chromatin remodeling. SCM contains two approximately 100-residue malignant brain tumor (MBT) repeats at the N terminus. These repeats are also found in other proteins involved in transcriptional repression. Here, we report the 1.78-A crystal structure of the two MBT repeats of SCM-like 2 (SCML2), a human homologue of SCM. Each repeat consists of an extended arm and a beta-barrel core. There are significant structural similarities to the Tudor, PWWP, and chromo domains, suggesting probable evolutionary relationships and functional similarities between the MBT repeats and these domains.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Chromosomal Proteins, Non-Histone
  • Crystallization
  • Crystallography, X-Ray
  • DNA-Binding Proteins / chemistry*
  • Evolution, Molecular
  • Humans
  • Molecular Structure
  • Neoplasm Proteins / chemistry
  • Polycomb-Group Proteins
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Repetitive Sequences, Nucleic Acid*
  • Repressor Proteins / chemistry
  • Transcription Factors / chemistry*
  • Tumor Suppressor Proteins


  • Chromosomal Proteins, Non-Histone
  • DNA-Binding Proteins
  • L3MBTL1 protein, human
  • Neoplasm Proteins
  • Polycomb-Group Proteins
  • Repressor Proteins
  • SCML2 protein, human
  • Transcription Factors
  • Tumor Suppressor Proteins

Associated data

  • PDB/1O11