Cell Biology International Reports, Vol. 74, No. 1, January 1990 69 GENES BBSPGBSIVE TOTBEALTEBATION OF PGLYAHINB BIOSYBTBBSIS IN NNUROSPONA CBASSA Grotewold, E., Aisemberg, G.O., Taccioli, G.E., and Judewicz, N.D.* Instituto de Investigaciones en Ingenieria Genetica y Biologia Molecular (INGEBI), Vuelta de Obligado 2490, 1428 Buenos Aires, Argentina. * Correspondence to be addressed to Dr N.D. Judewicz, Institut de Microbiologic, Batiment 409 Universit# Paris-Sud, Centre D'Orsay, 91405 Orsay Cedex, France. Key words: polyamine deficiency - ODC-ase inhibition - gene activation - Neurospora crassa ABSTRACT Wild-type Neurospora crassa grown in minimal medium was exposed to -difluormethyl ornithine (DFMO), a specific inhibitor of ornithine-decarboxylase (ODC-ase) activity. Protein-synthesis rates impaired by DFMO were restored by the addition of spermidine. The pattern on SDS-acry- lamide gels displayed three newly synthesized poly- peptides, ~27, p31 and p99 after DFMO action in the absence of exogenous polyamine. The ODC-ase mutant (soe- 1) grown in spermidine-supplemented medium did not show an induced polypeptide pattern. The lack of ODC-ase activity promotes the expression of p27- and p31-coding genes in both strains but transcription of p31 gene is shut-off after spermidine addition. Both transcripts are also accumulated after exposure to low cycloheximide doses or nutrient starvation. Another cycloheximide- inducible gene coding for p70 is also expressed under DFMO-treatment. IBTBODTJCTION Polyamine function in eucaryotic cells is still obscure even though they constitute an essential element for normal growth and development. The role of polyamine in ENA synthesis, tENA splicing and binding to tBNA in vitro, have been investigated (for a review see Tabor and Tabor, 1984) but their involvement in protein bio- synthesis, mainly on translation fidelity, should be emphasized. In lower eucaryotes, the availability of a variety of mutants has permitted an insight into the physiological function of polyamines. In Neurospora crassa, putrescine and spermidine are synthesized 0309-1651/90/010069-10/$03.00/O @ 1990 Academic Press Ltd.