Mechanism of hsp70i gene bookmarking.

In contrast to most genomic DNA in mitotic cells, the promoter regions of some genes, such as the stress-inducible hsp70i gene that codes for a heat shock protein, remain uncompacted, a phenomenon called bookmarking. Here we show that hsp70i bookmarking is mediated by a transcription factor called HSF2, which binds this promoter in mitotic cells, recruits protein phosphatase 2A, and interacts with the CAP-G subunit of the condensin enzyme to promote efficient dephosphorylation and inactivation of condensin complexes in the vicinity, thereby preventing compaction at this site. Blocking HSF2-mediated bookmarking by HSF2 RNA interference decreases hsp70i induction and survival of stressed cells in the G1 phase, which demonstrates the biological importance of gene bookmarking.

Use of a modified yeast one-hybrid screen to identify BAF60a interactions with the Vitamin D receptor heterodimer.

A modified yeast one-hybrid screen was used to isolate proteins capable of interacting with the Vitamin D receptor (VDR) heterodimer complex while driving expression from a repressor Vitamin D response element (VDRE). Four of nine independent colonies recovered in the screen coded for full-length BAF60a, a component of the mammalian SWI/SNF complex. Deletion studies in yeast were unable to localize a unique region of BAF60a responsible for interaction with the heterodimer complex, as only the full-length protein would support reporter gene expression.

Structural and topological studies on the lipid-mediated assembly of a membrane-associated lipomannan in Micrococcus luteus.

The biosynthesis of three mannolipids and the presence of a membrane-associated lipomannan in Micrococcus luteus (formerly Micrococcus lysodeikticus) were documented over 30 years ago. Structural and topological studies have been conducted to learn more about the possible role of the mannolipids in the assembly of the lipomannan. The major mannolipid has been purified and characterized as alpha-D-mannosyl-(1 --> 3)-alpha-D-mannosyl-(1 --> 3)-diacylglycerol (Man2-DAG) by negative-ion electrospray-ionization multistage mass spectrometry (ESI-MSn).

Interaction between protein phosphatase 2A and members of the importin beta superfamily.

While performing a yeast two-hybrid library screen to uncover novel PP2A-interacting proteins, we discovered a specific interaction between a member of the importin beta/karyopherin beta superfamily, importin 9, and the A subunit of PP2A (PR65). This interaction between importin 9 and the A subunit was confirmed by in vitro pulldown, immunoprecipitation, and microcystin-Sepharose chromatography. We also found that another family member, importin beta, interacted specifically with the A subunit of PP2A.