GATA-1, a transcription factor essential for the development of the erythroid lineage, contains two adjacent highly conserved zinc finger motifs. The carboxy-terminal finger is necessary and sufficient for specific binding to the consensus GATA recognition sequence: mutant proteins containing only the amino-terminal finger do not bind. Here we identify a DNA sequence (GATApal) for which the GATA-1 amino-terminal finger makes a critical contribution to the strength of binding. The site occurs in the GATA-1 gene promoters of chickens, mice, and humans but occurs very infrequently in other vertebrate genes known to be regulated by GATA proteins. GATApal is a palindromic site composed of one complete [(A/T)GATA(A/G)] and one partial (GAT) canonical motif. Deletion of the partial motif changes the site to a normal GATA site and also reduces by as much as eightfold the activity of the GATA-1 promoter in an erythroid precursor cell. We propose that GATApal is important for positive regulation of GATA-1 expression in erythroid cells.

Urbanization negatively affects natural ecosystems in many ways, and aquatic systems in partic- ular. Urbanization is also cited as one of the potential contributors to recent dramatic declines in amphibian populations. From 2000 to 2002 we determined the distribution and abundance of native amphibians and exotic predators and characterized stream habitat and invertebrate communities in 35 streams in an urbanized landscape north of Los Angeles (U.S.A.). We measured watershed development as the percentage of area within each watershed occupied by urban land uses. Streams in more developed watersheds often had exotic crayfish ( Procambarus clarkii) and fish, and had fewer native species such as California newts ( Taricha torosa) and California treefrogs ( Hyla cadaverina). These effects seemed particularly evident above 8% development, a result coincident with other urban stream studies that show negative impacts beginning at 10-15% urbanization. For Pacific treefrogs ( H. regilla), the most widespread native amphibian, abundance was lower in the presence of exotic crayfish, although direct urbanization effects were not found. Benthic macroinvertebrate communities were also less diverse in urban streams, especially for sensitive species. Faunal community changes in urban streams may be related to changes in physical stream habitat, such as fewer pool and more run habitats and increased water depth and flow, leading to more permanent streams. Variation in stream permanence was particularly evident in 2002, a dry year when many natural streams were dry but urban streams were relatively unchanged. Urbanization has significantly altered stream habitat in this region and may enhance invasion by exotic species and negatively affect diversity and abundance of native amphibians. Efectos de la Urbanización sobre la Distribución y Abundancia de Anfibios y Especies Invasoras en Arroyos del Sur de California Resumen: La urbanización afecta de muchas formas negativas a los ecosistemas naturales, particularmente a los sistemas acuáticos. La urbanización también está reconocida como uno de los potenciales causantes de las dramáticas declinaciones recientes en las poblaciones de anfibios. Entre 2000 y 2002 determinamos la distribución y abundancia de anfibios nativos y depredadores exóticos y caracterizamos el hábitat y las comunidades de invertebrados en 35 arroyos en un paisaje urbanizado al norte de LosÁngeles. Medimos el desarrollo de la cuenca como el porcentaje de la superficie ocupada por usos urbanos en cada cuenca. ‡ ‡email seth riley@nps.gov † †Current address: Environmental Science and Policy, Riley et al. Urbanization and Stream Amphibians 1895Los arroyos en cuencas más desarrolladas a menudo tenían cangrejos de río exóticos (Procambarus clarkii) y peces, y tenían menos especies nativas, como tritones (Taricha torosa) y ranas arborícolas (Hyla cadaverina). Estos efectos parecieron particularmente evidentes arriba de 8% de desarrollo, un resultado que coincide con otros estudios de arroyos urbanos que muestran impactos ...

Hemoglobin was first observed in neural tissue of invertebrates by Lankester (3) who noted the brilliant crimson color of the ganglia of the polychaetous annelid Aphrodite aculeata. Neural Hbs have since been recorded in or associated with nervous tissue of other annelids (4 -7), molluscs (5, 8 -12), arthropods (13, 14), and nemerteans (15,16 et al. (19) isolated and determined the amino acid sequence of the Hb from the neural tissue of A. aculeata. They found that the Hb was dimeric and had a relatively high O 2 affinity and that the sequence and gene structure clearly showed it to be a member of the globin family.Many nemertean worms express intracellular Hbs in red blood cells, body wall muscle tissue, and neural tissue. We report here the amino acid sequences, gene structure, and oxygen equilibria in situ for both the body wall and the neural tissue Hbs of the marine nemertean, Cerebratulus lacteus. We also propose a role of the neural hemoglobin as an oxygen store. We have used the amino acid sequences of the globins in maximum parsimony analyses to address possible phylogenetic relationships. These Hbs are very small, yet stable, unlike the artificially truncated mini-Mbs (20 -22). This finding should make the C. lacteus Hbs particularly valuable for studies of folding and stability. EXPERIMENTAL PROCEDURES Animals and Tissue PreparationEighty-four specimens of C. lacteus were purchased from the Department of Marine Resources, Marine Biological Laboratories, Woods Hole, MA, and maintained at 4°C in the laboratory in 0.45 m of filtered seawater. Animals used for oxygen-binding experiments were kept a maximum of 2 weeks. Tissue samples needed for protein, RNA, and DNA experiments were dissected from animals within 72 h of delivery, immediately frozen in a dry ice/ethanol bath, and stored at Ϫ80°C. Tissues were prepared for microscopy by relaxing the animals in MgCl 2 isotonic to seawater and fixing the head and trunk segments in 2.5% glutaraldehyde in 200 mM phosphate buffer, pH 7.4, made isotonic (0.58 M) by addition of NaCl. Segments were postfixed in 1.0% osmium tetroxide in the same buffer, dehydrated in an ethanol series, and embedded in Epon 812 resin. Ultrathin sections were stained with methylene blue and examined by light microscopy. Isolation and Purification of HemoglobinsHb-containing tissues were ground in liquid N 2 , then transferred to 50 mM Tris acetate, 10 mM EDTA, pH 7.5, at 0°C, followed by centrifugation at 12,000 ϫ g for 10 min at 4°C. Brain and lateral nerve tissue extracts are referred to as neural Hb, and body wall muscle extracts are referred to as body wall Hb. Tissue extracts were stored at 0°C if used immediately or refrozen in liquid N 2 and stored at Ϫ80°C. Hbs were purified first by size-exclusion chromatography with G-75-SF Sephadex (Sigma) in a column (12 ϫ 450 mm) equilibrated at 4°C with 50 mM Tris acetate, 10 mM EDTA, pH 7.4 (measured at room temperature). Hbcontaining fractions from this column were pooled, dialyzed against 10

Red cells of the clam Barbatia reeveana express two hemoglobins, one composed of 16-to 17-kDa chains and the other of 35-kDa chains. The nucleotide sequence of the cDNA encoding the 35-kDa chain shows that the polypeptide has two very similar heme-binding domains, which are joined without use of an additional bridging sequence. Two novel introns occur in the gene for the two-domain globin: one, the "preceding" intron, is located two bases 5' from the start codon, and the other, a "bridge" intron, separates the DNA sequences encoding the two domains. Close correspondence exists between the 3' end of the preceding intron and the 3' end of the bridge intron and between parts of the 3' noncoding region of the cDNA for the two-domain globin and the 5' end of the bridge intron. These observations indicate that the bridge intron arose by unequal crossing-over between two identical or very similar genes for a single-domain globin. This conclusion, together with the proposal that exons were initially independent "minigenes" [Gilbert, W. (1987) and COOH termini of proteins and provides an explanation for the observation that splice junctions usually map to protein surfaces. They do so because most NH2-and COOH-terminal residues are usually located on or near the surfaces of proteins.

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