InterPro domain: IPR005172

The following proteins of the tesmin/TSO1 family contain two cysteines-richrepeats with the consensus C-X-C-X(4)-C-X(3)-Y-C-X-C-X(6)-C-X(3)-C-X-C-X(2)-Cseparated by a region of variable length containing the short conservedsequence R-N-P-X-A-F-X-P-K:

• Animal tesmin or MTL5, originally identified by its specific expression in testes, but subsequently it was also detected at specific stages of ovary development.
• Animal tesmin-like (tesl) or LIN54.
• Drosophila melanogaster tombola (tomb), a meiotic arrest protein which is expressed specifically in testis.
• Arabidopsis thaliana TSO1, 'tso' means 'ugly' in Chinese and refers to the appearance of tso1 mutant flowers.
• Arabidopsis thaliana TSO1-like 1 and 2 (SOL1 and SOL2).
• Legume Cysteine-rich Polycomb-like Protein 1 (CPP1), a DNA-binding protein acting as a negative regulator of the leghemoglobin gene.

This domain has been named the CRC domain (C1-RNPXAFXPK-C2). It binds zinc andis able to bind DNA [ 1 , 2 , 3 , 4 , 5 ].The CRC domain shows some similarity to the CXC domain found in the E(z)-typeof Polycomb group proteins [ 6 ]. However, a clear distinctioncan be made, since the CXC domain lacks the RNPXAFXPK motif.

1. Regulation of meristem organization and cell division by TSO1, an Arabidopsis gene with cysteine-rich repeats. Development 127, 2207-17
2. TSO1 is a novel protein that modulates cytokinesis and cell expansion in Arabidopsis. Development 127, 2219-26
3. CPP1, a DNA-binding protein involved in the expression of a soybean leghemoglobin c3 gene. Proc. Natl. Acad. Sci. U.S.A. 97, 8163-8
4. The conserved cysteine-rich domain of a tesmin/TSO1-like protein binds zinc in vitro and TSO1 is required for both male and female fertility in Arabidopsis thaliana. J. Exp. Bot. 58, 3657-70
5. Tombola, a tesmin/TSO1-family protein, regulates transcriptional activation in the Drosophila male germline and physically interacts with always early. Development 134, 1549-59
6. Cloning and expression of a human/mouse Polycomb group gene, ENX-2/Enx-2. Biochim. Biophys. Acta 1395, 151-8