A DNA uptake-stimulating protein increases the antiproliferative effect of c-myb antisense oligonucleotide on leukemic cells.

Proliferation of HL-60 and MOLT4 leukemia cells was inhibited by a c-myb antisense oligonucleotide (ASO) in the presence of a DNA uptake-stimulating protein (DNA uptake-stimulating factor, DUSF). The inhibitory effect was very mild in the absence of DUSF. Sense oligonucleotides or DUSF, alone or in combination, were found to be ineffective. Cellular expression of the c-myb protein was significantly more inhibited by the c-myb ASO in the presence than in the absence of DUSF. In the presence of DUSF, c-myb protein practically disappeared from the nuclei of HL-60 and MOLT4 cells treated with the ASO. Thus, DUSF appears to effectively stimulate the uptake of c-myb ASO into tumor cells in vitro, augmenting its antiproliferative effect by decreasing c-myb expression.

Expression of protein phosphatase 1 during the asexual development of Neurospora crassa.

We cloned and sequenced the cDNA and the gene encoding the catalytic subunit of protein phosphatase 1 from the filamentous fungus Neurospora crassa. The gene, designated ppp-1 (phosphoprotein phosphatase 1), was mapped by restriction fragment length polymorphism to linkage group III, in the vicinity of con-7 and trp-1. The expression of the gene was monitored by reverse transcriptase and polymerase chain reactions, by Western blotting, and by protein phosphatase activity assays in synchronized cultures. Transcripts of ppp-1 were detected in the dormant conidia. The abundance of ppp-1 mRNA, Ppp-1 protein, and the activity of protein phosphatase 1 increased during germination and subsequent hyphal elongation as well as during the early stages of aerial mycelium formation.