We have isolated and sequenced genomic DNA clones covering the coding region of the chicken mid-size neurofilament (NF-M) gene and greater than 1 kb of its 5' upstream region. The NF-M gene contains two introns which both are located within the highly conserved C-terminal region of the rod domain. The 5' end of the corresponding mRNA was assigned to a G residue 40 nucleotides upstream of the translation start site and in appropriate distance from a potential TATA box. To functionally analyze the NF-M promoter, constructs carrying 112, 222, and 1026 nucleotides of the 5' upstream region in front of a luciferase reporter gene were tested for their capability to direct luciferase expression after transient transfection into various cell lines. Significant luciferase activity was recorded both in rat phaeochromocytoma (PC12) cells and murine fibroblasts. In PC12 cells, in which neurite outgrowth is induced by nerve growth factor (NGF), expression was stimulated up to 13-fold within 3 days of NGF treatment. This closely resembles expression of the endogenous NF-M gene in response to this hormone.

Prosomes are small cytoplasmic RNP complexes associated with repressed mRNA. In in vitro translation, they discriminate between the mRNA of adenovirus‐infected HeLa cells and those of uninfected cells grown under normal conditions. Prosomes as well as their RNA constituents interact much more strongly with poly(A)+ mRNA of infected cells and inhibit their translation in vitro preferentially. A possible role of prosomes in the differential regulation of translation is discussed.

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Prosomes, small cytoplasmic particles of mouse erythroblasts were found to contain low molecular weight RNA molecules in the range of 80 nucleotides. Nuclease digestion of prosomes suggests that prosomal proteins cover and protect almost the whole length of their RNA(s). Our results demonstrate clearly that RNA is an intrinsic component of prosomes.