RESUMO
A cDNA from metallothionein (MT) messenger RNA was identified in a library representing mRNA transcripts that are abundant in starving Atlantic cod larvae. The cod MT cDNA is closely related to MT mRNAs from other fish species and codes for a predicted 60 amino acid peptide. In adult cod liver MT mRNA is abundant and it is detected in cod eggs and larvae. Levels of MT mRNA were four times higher in three-week-old cod larvae starved for six days than in fed larvae, while starvation of four-week-old larvae for eight days resulted in a nearly seven-fold elevation in MT mRNA levels.
Assuntos
Peixes/genética , Metalotioneína/genética , RNA Mensageiro/genética , Inanição , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , DNA Complementar , Expressão Gênica , Dados de Sequência Molecular , RNA Mensageiro/metabolismo , Homologia de Sequência de AminoácidosRESUMO
Sequence-directed DNA curvature is most commonly associated with AA dinucleotides in the form of polyadenine runs. We demonstrate inherent curvature in DNA which lacks AA/TT dinucleotides using the criteria of polyacrylamide gel mobility and efficiency of DNA cyclization. These studies are based upon two 21-base pair synthetic DNA fragments designed to exhibit fixed curvature according to deflections made to the helical axis by non-AA dinucleotide stacks. Repeats of these sequences display anomalously slow migration in polyacrylamide gels. Moreover, both sequences describe helical conformations that are closed into circles by DNA ligase at much smaller sizes than is typical of nondeformed DNA. Chemical cleavage of these DNA molecules with hydroxyl radical is also consistent with local variation in helical conformation at specific dinucleotide steps.
Assuntos
DNA/química , Poli A/química , Autorradiografia , Sequência de Bases , Eletroforese em Gel Bidimensional , Eletroforese em Gel de Poliacrilamida , Hidróxidos/química , Radical Hidroxila , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Sequências Repetitivas de Ácido NucleicoRESUMO
In certain curved DNA fragments without AA dinucleotides, the gel retardation anomaly associated with curvature passes through a maximum with fragment length, indicating length (and electric field) dependent structural transitions in the DNA. We suggest that thermally induced stereochemical kinks in DNA are stabilized in the gel, thus relieving the effects of curvature. These kinks are shown to occur specifically at CA/TG and TA/TA stacks. Other physical and biological evidence points to frequent structural dislocations at CA and TA steps. These reversible sequence dependent kinks may therefore represent a novel class of structural protein-DNA recognition elements.
Assuntos
DNA/química , Sequência de Bases , Densitometria , Eletroquímica , Eletroforese em Gel de Poliacrilamida , Dados de Sequência Molecular , Conformação de Ácido Nucleico , TermodinâmicaRESUMO
Two restriction fragments of DNA containing the regulatory feature GTG/CAC were experimentally associated with core histones. The reconstituted DNA-histone complexes consisted of different forms of mononucleosomes. Lambda exonuclease and Fnu4HI were used to probe the structure of each distinct nucleoprotein complex. For each of the DNA fragments, one form of particle was produced that showed preferred placement of the core octamer on the DNA. The GTG/CAC base triplets may play some role in determining the final histone core positions in these reconstitutes.