Phosphorylation-dependent interaction of SATB1 and PIAS1 directs SUMO-regulated caspase cleavage of SATB1.

Special AT-rich sequence-binding protein 1 (SATB1) is a tissue-restricted genome organizer that provides a key link between DNA loop organization, chromatin modification/remodeling, and transcription factor association at matrix attachment regions (MARs). The SUMO E3 ligase PIAS1 enhances SUMO conjugation to SATB1 lysine-744, and this modification regulates caspase-6 mediated cleavage of SATB1 at promyelocytic leukemia nuclear bodies (PML NBs). Since this regulated caspase cleavage occurs on only a subset of SATB1, and the products are relatively stable, proteolysis likely mediates cellular processes other than programmed cell death.

SUMO conjugation to the matrix attachment region-binding protein, special AT-rich sequence-binding protein-1 (SATB1), targets SATB1 to promyelocytic nuclear bodies where it undergoes caspase cleavage.

SATB1 (special AT-rich sequence-binding protein-1) provides a key link between DNA loop organization, chromatin modification/remodeling, and association of transcription factors at matrix attachment regions (MARs). To investigate the role of SATB1 in cellular events, we performed a yeast two-hybrid screen that identified SUMO-1, Ubc9, and protein inhibitor of activated STAT (PIAS) family members as SATB1 interaction partners. These proteins, working in concert, enhanced SUMO conjugation to lysine-744 of SATB1.

The bcl-2 major breakpoint region (mbr) possesses transcriptional regulatory function.

The bcl-2 major breakpoint region (mbr), located within the 3'-UTR of the bcl-2 gene, is the site of the most common chromosomal translocation, t(14;18) (q32;q21), which occurs in follicular lymphoma. The mbr forms a triplex DNA structure under physiological conditions and the transcription factor special AT-rich sequence-binding protein 1 (SATB1) binds immediately downstream of the mbr. These observations raise the possibility that the mbr may be involved in regulation of bcl-2 gene expression.

Identification of a SUMO-binding motif that recognizes SUMO-modified proteins.

Posttranslational modification by the ubiquitin homologue, small ubiquitin-like modifier 1 (SUMO-1), has been established as an important regulatory mechanism. However, in most cases it is not clear how sumoylation regulates various cellular functions. Emerging evidence suggests that sumoylation may play a general role in regulating protein-protein interactions, as shown in RanBP2/Nup358 and RanGAP1 interaction.

Specific interaction of PML bodies with the TP53 locus in Jurkat interphase nuclei.

PML bodies play an important role in multiple pathways of growth control, such as transformation suppression, apoptosis, and Ras-induced senescence. However, the molecular and biological bases for these physiological phenomena are not well understood. The findings that viruses transcribe their genomes adjacent to PML bodies and that nascent RNA accumulates at their periphery have suggested that PML bodies are transcription-permissible domains.

The thymocyte-specific MAR binding protein, SATB1, interacts in vitro with a novel variant of DNA-directed RNA polymerase II, subunit 11.

A yeast two-hybrid screen of a Jurkat (T cell) derived cDNA library, using SATB1 (a matrix attachment region binding protein) as the bait, yielded four independent isolates of a novel variant of the DNA directed RNA polymerase II, subunit 11 (RPB11). Absence of lysine-17 from the amino terminus of this variant cannot be explained by alternative mRNA splicing. Instead, allele-specific PCR, combined with GenBank database searches, suggests that a recent gene duplication event has resulted in distinct loci encoding three variant forms of RPB11.