SummaryXenopus egg extract supports all the major cell-cycle transitions in vitro. We have used a proteomics approach to identify proteins whose abundance on chromatin changes during the course of an in vitro cell cycle. One of the proteins we identified was ELYS/MEL-28, which has recently been described as the earliest-acting factor known to be required for nuclear pore complex (NPC) assembly [1–4]. ELYS interacts with the Nup107-160 complex and is required for its association with chromatin. ELYS contains an AT-hook domain, which we show binds to chromatin with a high affinity. This domain can compete with full-length ELYS for chromatin association, thereby blocking NPC assembly. This provides evidence that ELYS interacts directly with chromatin and that this interaction is essential for NPC assembly and compartmentalization of chromosomal DNA within the cell. Furthermore, we detected a physical association on chromatin between ELYS and the Mcm2-7 replication-licensing proteins. ELYS chromatin loading, NPC assembly, and nuclear growth were delayed when Mcm2-7 was prevented from loading onto chromatin. Because nuclear assembly is required to shut down licensing prior to entry into S phase, our results suggest a mechanism by which these two early cell-cycle events are coordinated with one another.

The peroxisome proliferator-activated receptors (PPARs) are a family of fatty acid-activated transcription factors which control lipid homeostasis and cellular differentiation. PPAR␣ (NR1C1) controls lipid oxidation and clearance in hepatocytes and PPAR␥ (NR1C3) promotes preadipocyte differentiation and lipogenesis. Drugs that activate PPAR␣ are effective in lowering plasma levels of lipids and have been used in the management of hyperlipidemia. PPAR␥ agonists increase insulin sensitivity and are used in the management of type 2 diabetes. In contrast, there are no marketed drugs that selectively target PPAR␦ (NR1C2) and the physiological roles of PPAR␦ are unclear. In this report we demonstrate that the expression of PPAR␦ is increased during the differentiation of human macrophages in vitro. In addition, a highly selective agonist of PPAR␦ (compound F) promotes lipid accumulation in primary human macrophages and in macrophages derived from the human monocytic cell line, THP-1. Compound F increases the expression of genes involved in lipid uptake and storage such as the class A and B scavenger receptors (SRA, CD36) and adipophilin. PPAR␦ activation also represses key genes involved in lipid metabolism and efflux, i.e. cholesterol 27-hydroxylase and apolipoprotein E. We have generated THP-1 sublines that overexpress PPAR␦ and have confirmed that PPAR␦ is a powerful promoter of macrophage lipid accumulation. These data suggest that PPAR␦ may play a role in the pathology of diseases associated with lipidfilled macrophages, such as atherosclerosis, arthritis, and neurodegeneration.

Sds22 defines protein phosphatase 1 location and function at kinetochores and subsequent activity of aurora B in mitosis.