Crafford A. Harris

Detergent-salt resistance of LAP2α in interphase nuclei and phosphorylation-dependent association with chromosomes early in nuclear assembly implies functions in nuclear structure dynamics

Lamina‐associated polypeptide (LAP) 2 of the inner nuclear membrane (now LAP2β) and LAP2α are related proteins produced by alternative splicing, and contain a common 187 amino acid N‐terminal domain. We show here that, unlike LAP2β, LAP2α behaved like a nuclear non‐membrane protein in subcellular fractionation studies and was localized throughout the nuclear interior in interphase cells. It co‐fractionated with LAP2β in nuclear lamina/matrix‐enriched fractions upon extraction of nuclei with detergent, salt and nucleases. During metaphase LAP2α dissociated from chromosomes and became concentrated around the spindle poles. Furthermore, LAP2α was mitotically phosphorylated, and phosphorylation correlated with increased LAP2α solubility upon extraction of cells in physiological buffers. LAP2α relocated to distinct sites around chromosomes at early stages of nuclear reassembly and intermediarily co‐localized with peripheral lamin B and intranuclear lamin A structures at telophase. During in vitro nuclear assembly LAP2α was dephosphorylated and assembled into insoluble chromatin‐associated structures, and recombinant LAP2α was found to interact with chromosomes in vitro. Some LAP2α may also associate with membranes prior to chromatin attachment. Altogether the data suggest a role of LAP2α in post‐mitotic nuclear assembly and in the dynamic structural organization of the nucleus.

Nitroarylhydroxymethylphosphonic acids as inhibitors of CD45

A series of nitroarylhydroxymethylphosphonic acids was synthesized and evaluated as inhibitors of CD45. It was discovered that both the alpha hydroxy and nitro groups are essential for activity. Potency is enhanced by the addition of a large lipophilic group on the aryl ring adjacent to the phosphonic acid moiety. Kinetics studies have shown that these compounds are competitive inhibitors and thus bind at the active site of this enzyme.

The development of novel and selective p56lck tyrosine kinase inhibitors

Early T-cell receptor mediated signal transduction involves the activation of several tyrosine protein kinases. One of these tyrosine kinases, p56lck, is expressed primarily in T-cells and Natural Killer (NK) cells and has been shown to be critical for their proliferative and effector functions. Indandiones have been identified as a potent and selective chemical class that inhibits p56lck.