RESUMO
Chemokines are small, inducible, structurally related proteins that guide cells expressing the right chemokine receptors to sites of immune response. They have been identified and studied extensively in mammals, but little is known about their presence in other vertebrate groups. Here we describe seven new chemokines in bony fish and one in a cartilaginous fish, as well as one chemokine receptor in a jawless vertebrate. All eight chemokines belong to the SCYA (CC) subfamily characterized by four conserved cysteine residues of which the first two are adjacent. The chemokine receptor is of the CXCR4 type. Phylogenetic analysis does not reveal any clear evidence of orthology of fish and human chemokines. Although the divergence of the subfamilies began before the fish-tetrapod split, much of the divergence within the subfamilies took place separately in the two vertebrate groups. The existence of a chemokine receptor in the lamprey indicates that chemokines are apparently also present in the Agnatha.
Assuntos
Quimiocinas CC/genética , Peixes/genética , Peixes/imunologia , Receptores CXCR4/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Ciclídeos/genética , Ciclídeos/imunologia , DNA Complementar/genética , Humanos , Lampreias/genética , Lampreias/imunologia , Dados de Sequência Molecular , Filogenia , Homologia de Sequência de Aminoácidos , Tubarões/genética , Tubarões/imunologia , Especificidade da EspécieRESUMO
An expressed sequence tag obtained from a sea lamprey ( Petromyzon marinus) cDNA library was used to obtain a full-length coding sequence showing significant similarity to ABCB transporter proteins. The sequence is closely related to the mammalian ABCB9 protein and the TAP1 and TAP2 proteins that transport peptides for loading onto nascent Mhc class I molecules. The Pema-ABCB9 gene has an exon-intron organization similar to that of the mammalian TAP genes, with the exception of exon 2, which in the lamprey is split into two by a 949-bp long intron. The gene probably occurs in a single copy in the haploid lamprey genome. The ABCB9 genes appear to be evolving four-to-ten times slower than the TAP1 and TAP2 genes. Six putative transmembrane helices and the nucleotide-binding domain of the lamprey ABCB9 protein show high sequence similarity with the TAP1 and TAP2 molecules. The lamprey protein also contains sequence stretches that resemble the putative peptide interacting parts of the TAP1 and TAP2 molecules, but are peppered with ABCB9-specific residues.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Lampreias/genética , Membro 2 da Subfamília B de Transportadores de Cassetes de Ligação de ATP , Membro 3 da Subfamília B de Transportadores de Cassetes de Ligação de ATP , Sequência de Aminoácidos , Animais , Sequência de Bases , Transporte Biológico , Southern Blotting , Clonagem Molecular , Primers do DNA/química , Éxons , Biblioteca Gênica , Humanos , Íntrons , Dados de Sequência Molecular , Filogenia , Regiões Promotoras Genéticas , Ligação Proteica , RNA/genética , RNA/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de AminoácidosRESUMO
The macrophage migration inhibitory factor (MIF) is a cytokine produced by T lymphocytes and macrophages in response to inflammatory stimuli. We sequenced MIF cDNA clones of two jawless fishes, the sea lamprey (Petromyzon marinus) and the North Atlantic hagfish (Myxine glutinosa), as well as of the jawed (cichlid) fish Paralabidochromis chilotes. The fish MIF-encoding genes have the same exon-intron organization as the mammalian MIF genes and are present in one copy per haploid genome. Secondary and tertiary structure predictions suggest that the fish MIF proteins have a topology characteristic of the entire MIF-family of proteins. Phylogenetic analysis separates the known nematode members of the family into two groups, one having a sister group relationship with the mammalian D-dopachrome tautomerase (DDT) proteins and the other being related to vertebrate MIFs. It also reveals a high degree of convergent evolution among the members of the family. Finally, it suggests that the divergence of MIF and DDT occurred before the emergence of nematodes in metazoan evolution.
Assuntos
Ciclídeos/classificação , Evolução Molecular , Feiticeiras (Peixe)/classificação , Lampreias/classificação , Fatores Inibidores da Migração de Macrófagos/classificação , Sequência de Aminoácidos , Animais , Sequência de Bases , Ciclídeos/genética , Feiticeiras (Peixe)/genética , Lampreias/genética , Fatores Inibidores da Migração de Macrófagos/genética , Dados de Sequência Molecular , Filogenia , Alinhamento de SequênciaRESUMO
Gene frequencies of eight Siberian populations (Mansi, Tuva, Todja, Tofalar, Buryat, Okhotsk Evenki, Ulchi, and Negidal) were determined for the three most polymorphic HLA class II loci ( DRB1, DQA1, and DQB1) by a combination of single-stranded conformational polymorphism typing and DNA sequencing. The number of alleles per population ranged from 16 to 25, from seven to eight, and from nine to 14 for the DRB1, DQA1, and DQB1 loci, respectively. The alleles at the three loci occurred in 66 different combinations (haplotypes), most of which appeared to be of ancient origin, but some may have arisen within the Siberian populations. Phylogenetic analysis of the frequency data suggests that the HLA genes of Asian and indigenous American populations stem from a single pool distinct from the gene pools of European and African populations. The Asian populations separate into two clusters, one of which encompasses nearly all the Siberian populations and all the indigenous American populations tested, while the other consists of Central, Eastern, and Southeastern Asian populations. The position of the Tuva people appears to be near the node from which the two clusters diverge. The divergence time of the two clusters is estimated to be 21,000-24,000 years BP. Three different branches of the native Siberian peoples seem to have contributed founders for the indigenous American ethnic groups.
