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Results for “gene expression evolution”

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PubMed1980

Transcriptional control regions of the adenovirus VAI RNA gene.

By constructing deletion mutations in cloned adenovirus types 2 and 5 VAI genes and measuring the ability of altered templates to direct transcription of VAI RNA in HeLa cell extracts, we have located two transcriptional control regions. The first is an intragenic region located between positions +9 and +72 relative to the 5' end of the VAI(A) RNA. Those deletions examined within these sequences abolished the transcription of mutant templates in HeLa cell extracts. The second control region includes 5' flanking sequences which abut the VAI coding region. Mutations here can reduce the efficiency with which the VAI gene is transcribed. Nucleotide sequence similarities were noted on comparison of the VAI intragenic control region to tRNA sequences, which lead us to speculate that the transcriptional regulation of these two types of genes may be quite similar; the adenovirus VA genes may even have evolved from a tRNA gene(s).

Adenoviruses, Human↗
PubMed1983

The Xenopus laevis globin gene family: chromosomal arrangement and gene structure.

Clones containing nine different larval and adult globin genes have been isolated from two genomic libraries of Xenopus laevis. They encompass three distinct DNA regions: a 70 kb region containing five genes in the order 5'-alpha Lla-alpha Llb-alpha Al-beta Al-beta Lla-3', all with the same transcriptional polarity; a 40 kb region with three genes, 5'-alpha Llla-alpha Lllb-alpha All-3', again with the same polarity; and a 10 kb segment comprising the beta Llla gene only. The beta All gene has not been found in our libraries. Genetic analysis has revealed two more beta L genes (beta Lllb, beta Lllb). Globin-like sequences have also been isolated, but have not been further characterized. The X. laevis globin gene family thus consists of 12 genes arranged in two clusters, each containing larval and adult alpha and beta genes in a unique, "symmetrical" arrangement. Electron microscopic analysis has revealed that Xenopus globin genes also comprise three exons and two introns, but differ from the globin genes of higher vertebrates in that the introns are much larger.

Animals↗
PubMed1986

Some guidelines for identification of recognition sequences: regulatory sequences frequently contain (T)GTG/CAC(A), TGA/TCA and (T)CTC/GAG(A).

Inspection of many proposed recognition signal sequences shows that TGTG/CACA, GAGA/TCTC or their triplet subsets, and TGA/TCA occur frequently. These repeated elements, conserved in recognition sequences from evolutionarily distant organisms, are likely to possess unique structural characteristics. Recurrence of these oligomers may aid in identification of further regulatory sequences in upstream or other regions. Another class of recognition sequences is GC-rich. At present there are only a few examples of this class. It is likely that these sequences function via a different mechanism.

Animals↗
PubMed1992

Structure of the Aspergillus nidulans qut repressor-encoding gene: implications for the regulation of transcription initiation.

The nucleotide (nt) sequence of the qutR gene has been determined and shown to encode an inferred protein (QUTR) of 929 amino acids (aa). The inferred aa sequence shows a high level of similarity throughout its length with the aa sequence of the three C-terminal domains (shikimate kinase; 3-dehydroquinase; shikimate dehydrogenase) of the pentafunctional AROM protein of Aspergillus nidulans that catalyses steps 2-6 in the shikimate pathway. The inferred QUTR aa sequence has a completely conserved aa sequence motif, Gly, Xaa4, Gly, Lys, Ser, that is found in proteins that bind purine nt, suggesting that the inferred protein may have an in vivo kinase activity. The inferred QUTR protein also has a peptide sequence, DMVRLTQPAT, related to the active-site peptide in type-I 3-dehydroquinases. In active 3-dehydroquinases, the Arg (of QUTR) is replaced by Lys, which is involved in Schiff base formation as part of the reaction mechanism. The change from Lys----Arg in the inferred QUTR protein may allow the protein to bind but not metabolise the substrate for 3-dehydroquinase enzymes, namely 3-dehydroquinate. These observations are entirely consistent with the genetical model for how the QUTR protein functions, as it predicts that the protein can recognise and bind, but not metabolise, quinate, 3-dehydroquinate, and dehydroshikimate.

Amino Acid Sequence↗
PubMed2006

Keynote lecture: an update on the what, why and how questions of ageing.

In this keynote address, we briefly consider three global questions on the biology of ageing. What is it? While it is certainly the case that development has a major impact upon ageing, gerontologists characterize ageing as gradual, insidious, post-maturational declines in the structure and function of multiple organ systems, certainly to include reproduction. This is accompanied by increasing rates of mortality within populations. Comprehensive, longitudinal physiological assessments are not commonly pursued in their experiments, however; this deficiency limits one's ability to interpret the results of putative interventions. Why does it happen? Although subject to recent challenges, the most satisfying explanation for inter-specific variations in longevity is given by the evolutionary biological theory of ageing. Life history parameters, including longevity, are molded by the ecological forces in which the species evolves. How does it happen? To gain insight into fundamental mechanisms of ageing, we have focused upon classes of gene actions that, according to the evolutionary theory, can escape the forces of natural selection.

Aged↗
PubMed2005

A decade of progress in understanding vitamin E synthesis in plants.

The chloroplasts of higher plants contain and elaborate many unique biochemical pathways that produce an astonishing array of compounds that are vital for plastid function and are also important from agricultural and nutritional perspectives. One such group of compounds is the tocochromanols (more commonly known as Vitamin E), which is a class of four tocopherols and four toctorienols, lipid-soluble antioxidants that are only synthesized by plants and other oxygenic, photosynthetic organisms. Though the essential nature of tocopherols in mammalian diets was recognized over 80 years ago and the biosynthetic pathway in plants and algae elucidated in the late 1970s and early 80s, it has only been in the past decade that the genes and proteins for tocopherol synthesis have finally been isolated and characterized. The use of model plant and cyanobacterial systems has driven this gene discovery to the point that manipulation of tocopherol levels and types in various plant tissues and crops is becoming a reality. This article reviews progress since 1996 in the molecular and genetic understanding of tocopherol synthesis in the model photosynthetic organisms Arabidopsis thaliana and Synechocystis PCC6803 as a primer for current and future efforts to manipulate the levels of this essential nutrient in food crops by breeding and transgenic approaches.

Arabidopsis↗
PubMed2006

Gene regulatory network models for plant development.

Accumulated genetic data are stimulating the use of mathematical and computational tools for studying the concerted action of genes during cell differentiation and morphogenetic processes. At the same time, network theory has flourished, enabling analyses of complex systems that have multiple elements and interactions. Reverse engineering methods that use genomic data or detailed experiments on gene interactions have been used to propose gene network architectures. Experiments on gene interactions incorporate enough detail for relatively small developmental modules and thus allow dynamical analyses that have direct functional interpretations. Generalities are beginning to emerge. For example, biological genetic networks are robust to environmental and genetic perturbations. Such dynamical studies also enable novel predictions that can lead to further experimental tests, which might then feedback to the theoretical analyses. This interplay is proving productive for understanding plant development. Finally, both experiments on gene interactions and theoretical analyses allow the identification of frequent or fixed evolutionary solutions to developmental problems, and thus are contributing to an understanding of the genetic basis of the evolution of development and body plan.

Biological Evolution↗
PubMed2003

Waddington's widget: Hsp90 and the inheritance of acquired characters.

Conrad Waddington published an influential model for evolution in his 1942 paper, Canalization of Development and Inheritance of Acquired Characters. In this classic, albeit controversial, paper, he proposed that an unknown mechanism exists that conceals phenotypic variation until the organism is stressed. Recent studies have proposed that the highly conserved chaperone Hsp90 could function as a "capacitor," or an "adaptively inducible canalizer," that masks silent phenotypic variation of either genetic or epigenetic origin. This review will discuss evidence for, and arguments against, the role of Hsp90 as a capacitor for morphological evolution, and as a key component of what we call "Waddington's widget."

Animals↗