Two previously identified Bacillus subtilis DNA segments, dciA and dciB, whose transcripts accumulate very rapidly after induction of sporulation, were found in the same 6.2 kb transcription unit, now known as the dciA operon. Analysis of the sequence of the dciA operon showed that its putative products are homologous to bacterial peptide transport systems. The product of the fifth gene, DciAE, is similar to peptide-binding proteins from Escherichia coli and Salmonella typhimurium (DppA and OppA) and B. subtilis (OppA). A null mutation in dciAE abolished the ability of a proline auxotroph to grow in a medium containing the dipeptide Pro-Gly as sole proline source, suggesting that the dciA operon encodes a dipeptide transport system.

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Serial analysis of gene expression (SAGE) was applied to the malarial parasite Plasmodium falciparum to characterize the comprehensive transcriptional profile of erythrocytic stages. A SAGE library of ϳ8335 tags representing 4866 different genes was generated from 3D7 strain parasites. Basic local alignment search tool analysis of high abundance SAGE tags revealed that a majority (88%) corresponded to 3D7 sequence, and despite the low complexity of the genome, 70% of these highly abundant tags matched unique loci. Characterization of these suggested the major metabolic pathways that are used by the organism under normal culture conditions. Furthermore several tags expressed at high abundance (30% of tags matching to unique loci of the 3D7 genome) were derived from previously uncharacterized open reading frames, demonstrating the use of SAGE in genome annotation. The open platform "profiling" nature of SAGE also lead to the important discovery of a novel transcriptional phenomenon in the malarial pathogen: a significant number of highly abundant tags that were derived from annotated genes (17%) corresponded to antisense transcripts. These SAGE data were validated by two independent means, strand specific reverse transcription-polymerase chain reaction and Northern analysis, where antisense messages were detected in both asexual and sexual stages. This finding has implications for transcriptional regulation of Plasmodium gene expression.

Enhancer elements regulating the neuronal gene, tyrosine hydroxylase (TH), were identified in TH-expressing peripheral nervous system PATH and central nervous system CATH cell lines. Mutational analysis in which rat TH 5-flanking sequences directed chloramphenicol acetyltransferase (CAT) reporter gene expression demonstrated that mutating the cyclic AMP response element (CRE) at ؊45 base pair reduced expression by 80 -90%. A CRE linked to an enhancerless TH promoter fully supported expression. Cotransfection of a dominant-negative CREB protein reduced expression 50 -60%, suggesting that the CRE is bound by CREB or a CREB dimerization partner. Although mutating the AP1/dyad (AD) element at ؊205 base pair only modestly reduced CAT levels, AD minimal enhancer constructs gave 45-80% of wild type expression when positioned at ؊91 or ؊95. However, in its native context at ؊205, the AD could not support expression. In contrast, a CRE, moved from its normal position at ؊45 to ؊206, gave full activity. These results indicate that the CRE is critical for TH transcription in central nervous system CATH and peripheral nervous system PATH cells, whereas the AD is less important and its enhancer activity is contextand/or position-dependent. These results represent the first attempts to map regulatory elements directing TH expression in central nervous system cell lines. Tyrosine hydroxylase (TH)1 converts L-tyrosine to 3,4-dihydroxy-L-phenylalanine and is the first and rate-limiting enzyme in catecholamine synthesis (Nagatsu et al., 1964;Levitt et al., 1965). TH is expressed in specific cell types in the peripheral and central nervous systems. Sympathetic ganglia and chromaffin cells of the adrenal medulla are major sites of peripheral TH expression. In the central nervous system, TH-expressing neurons are located in the diencephalon, midbrain, brainstem, olfactory bulb, and retina (Bjorklund and Lindvall, 1984).TH activity is regulated at the protein level and the RNA level. Activation at the protein level is short term with a time course of less than 1 h and mainly occurs via phosphorylation of preexisting protein molecules, which increases TH activity (reviewed by Zigmond et al. (1989)). Induction of TH at the mRNA level is long term, resulting in increased mRNA levels for hours to days. Long term increases of TH activity are induced by various physiological stimuli including cyclic AMP (cAMP), epidermal growth factor, glucocorticoids, nerve growth factor, transsynaptic neuronal activity, and depolarization. These inducers have been shown to increase TH mRNA levels, and several studies indicate that they increase mRNA levels by inducing transcription: cAMP (Lewis et al

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