Upon exposure to ethanol, Drosophila display behaviors that are similar to ethanol intoxication in rodents and humans. Using an inebriometer to measure ethanol-induced loss of postural control, we identified cheapdate, a mutant with enhanced sensitivity to ethanol. Genetic and molecular analyses revealed that cheapdate is an allele of the memory mutant amnesiac. amnesiac has been postulated to encode a neuropeptide that activates the cAMP pathway. Consistent with this, we find that enhanced ethanol sensitivity of cheapdate can be reversed by treatment with agents that increase cAMP levels or PKA activity. Conversely, genetic or pharmacological reduction in PKA activity results in increased sensitivity to ethanol. Taken together, our results provide functional evidence for the involvement of the cAMP signal transduction pathway in the behavioral response to intoxicating levels of ethanol.

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The adenovirus major late transcription unit (MLTU) encodes five colinear mRNA families, Li through L5, each distinguished by a unique poly(A) site. Site selection is regulated during the course of infection, predominating early at the Li site and late at the L2 through L5 sites. Two general mechanisms can be invoked to explain predominant usage of the Li site early in infection. MLTU The termini of almost all mRNAs in higher eucaryotes are distinguished by the presence of a poly(A) tail, a tract of 50 to 250 adenylic acids added to the 3' end. The addition site for the poly(A) tail is not generated by transcription termination; rather, it is formed by endonucleolytic cleavage of a primary transcript, or pre-mRNA, that can extend kilobases beyond the site (22, 52). The mechanisms that govern cleavage and poly(A) addition are under intense study. Physically distinct signals required for the process are located on either side of the poly(A) site (reviewed in reference 23). Located 10 to 30 nucleotides upstream of the site is the highly conserved hexanucleotide AAUAAA (21, 59). Mutational analyses of this element in vivo (35,49,71) and in vitro (15,33,72) demonstrate that it is absolutely required for cleavage and polyadenylation. Located 5 to 50 nucleotides downstream of the site is a less conserved GU-or U-rich signal. Small deletions, insertions, and point mutations within this region significantly reduce the efficiency of 3'-end processing (14,27,30,31,33,46,48,62,74).The biochemical study of cleavage and polyadenylation has revealed the presence of a large complex that binds specifically at the poly(A) site (36,65,(73)(74)(75) functional diversity in the proteins that are expressed. The mechanisms that control alternative processing decisions have been studied in several systems. At the calcitonin locus, tissue-specific usage of poly(A) and splice acceptor sites causes production of calcitonin in the thyroid gland and calcitonin gene-related peptide (CGRP) in neurons (5). The main processing decision in this system appears to be early commitment to the CGRP-specific splice site, which dictates subsequent poly(A) site usage (40). In the ,u heavy-chain locus, RNA processing choices regulate production of secreted and membrane-bound immunoglobulins during B-cell development: differential processing prevents production of the mRNA encoding the secreted form in mature plasma cells (4,18,61). Whether the dominant control mechanism is exerted at the level of poly(A) site selection (24,25), transcription termination (24), splice site-poly(A) site competition (56, 57), or some combination thereof is still being debated. Nevertheless, it is generally accepted that position and intrinsic strength of processing signals are critical for regulation.Temporal regulation of 3'-end formation is seen in the adenovirus major late transcription unit (MLTU), where five poly(A) sites define five colinear mRNA families, designated Li through L5 (42,47,53

nalyot (nal) is a novel olfactory memory mutant of Drosophila, encoding Adf1, a myb-related transcription factor. Following extended training sessions, Adf1 mutants show normal early memory but defective longterm memory. Adf1 shows widespread spatiotemporal expression, yet mutant alleles reveal no discernible disruptions in gross morphology of the nervous system. Studies at the larval neuromuscular junction, however, reveal a role for Adf1 in the modulation of synaptic growth-in contrast to the role established for dCREB2 in the control of synaptic function (Davis et al., 1996). These findings suggest that Adf1 and dCREB2 regulate distinct transcriptional cascades involved in terminal stages of synapse maturation. More generally, Adf1 provides a novel link between molecular mechanisms of developmental and behavioral plasticity.

In retroviral proviruses, the poly(A) site is present in both long terminal repeats (LTRs) but used only in the 3' position. One mechanism to account for this selective poly(A) site usage is that LTR U3 sequences, transcribed only from the 3' poly(A) site, are required in the RNA for efficient processing. To test this possibility, mutations were made in the human immunodeficiency virus type 1 (HIV-1) U3 region and the mutated LTRs were inserted into simple and complex transcription units. HIV-1 poly(A) site usage was then quantitated by Si nuclease analysis following transfection of each construct into human 293 cells. The results showed that U3 sequences confined to the transcription control region were required for efficient usage of the HIV-1 poly(A) site, even when it was placed 1.5 kb from the promoter. Although the roles of U3 in processing and transcription activation were separable, optimal 3' end formation was partly dependent on HIV-1 enhancer and SP1 binding site sequences.