Cell biology Evolution Intelligent Design

At Sci-News: Chromatin First Evolved in Ancient Microbes 1-2 Billion Years Ago, New Research Suggests

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Chromatin is the ensemble of genomic DNA and a large number of proteins. Despite its fundamental role in biology of eukaryotic cells, scientists lack a comprehensive understanding of chromatin evolution.

In almost every human cell, two meters-long DNA has to fit within a nucleus that is just 8 millionths of a meter wide. Like wool around a spool, the extreme space challenge requires DNA to wrap around structural proteins called histones. This coiled genetic architecture, known as chromatin, protects DNA from damage and has a key role in gene regulation.

Histones are present in both eukaryotes, living organisms that have specialized cellular machinery such as nuclei and microtubules, and archaea, another branch of the tree of life consisting of single-celled microbes that are prokaryotic, meaning they lack a nucleus.

In eukaryotic cells, histones are modified by enzymes, continuously shapeshifting the genomic landscape to regulate gene expression and other genomic processes. Despite this fundamental role, the exact origin of chromatin has been shrouded in mystery.

“Our results underscore that the structural and regulatory roles of chromatin are as old as eukaryotes themselves,” Dr. Grau-Bové said. “These functions are essential for eukaryotic life — since chromatin first appeared, it’s never been lost again in any life form.”

Chromatin, with its structural proteins (histones) apparently came into existence along with eukaryotic cells. Since the probability of forming even a single moderate protein by natural processes is too remote to be expected in our universe, the apparently simultaneous appearance of chromatin and eukaryotes is not consistent with an evolutionary explanation.

The scientists hypothesize that chromatin evolved in this microbe as a result of selective pressures in the primordial environment of Earth.

“Viruses and transposable elements are genome parasites that regularly attack DNA of single-celled organisms,” said Dr. Arnau Sebe-Pedrós, a researcher in the Centre for Genomic Regulation at the Barcelona Institute of Science and Technology. “This could have led to an evolutionary arms-race to protect the genome, resulting in the development of chromatin as a defensive mechanism in the cell that gave rise to all known eukaryotic life on Earth.”

“Later on, these mechanisms were co-opted into elaborate gene regulation, as we observe in modern eukaryotes, particularly multicellular organisms.”

The team’s paper was published in the journal Nature Ecology and Evolution.

Sci-News

6 Replies to “At Sci-News: Chromatin First Evolved in Ancient Microbes 1-2 Billion Years Ago, New Research Suggests

  1. 1
    bornagain77 says:

    DNA Wrapping (Histone Protein Wrapping to Cell Division)- video
    http://www.youtube.com/watch?v=gbSIBhFwQ4s

    Or related note:

    Genes and Organisms: Improvising the Dance of Life – Stephen L. Talbott – Nov. 10, 2015
    Excerpt: You may recall from my earlier article, “Getting Over the Code Delusion” (Talbott 2010), that packing DNA into a typical cell nucleus is like packing about 24 miles of very thin, double-stranded string into a tennis ball, with the string cut up (in the normal human case) into 46 pieces, corresponding to our 46 chromosomes.
    To locate a protein-coding gene of typical size within all that DNA is like homing in on a one-half-inch stretch within those 24 miles. Or, rather, two relevant half-inch stretches located on different pieces of string, since we typically have two copies of any given gene. Except that sometimes one copy differs from the other and one version is not supposed to be expressed, or one version needs to be expressed more than the other, or the product of one needs to be modified relative to the other. So part of the job may be to distinguish one of those half-inch stretches from the other. “Decisions” everywhere, it seems.
    But no such decisions are made in a vacuum. As it happens, the chromosome does not consist of a naked DNA double helix. Our DNA, rather, is bound up with a massive, intricate, and dynamic protein-RNA-small molecule complex (called chromatin) that is as fully “informative” for the cell as the DNA sequence itself — and, you might say, much more active and directive.,,,
    the cell, by managing the shifting patterns of the chromatin infrastructure within which DNA is embedded, brings our chromosomes into movement on widely varying scales. These include large looping movements that put particular genes into connection with essential regulatory sequences and with other, related genes (that is, with other one-half inch stretches of our “24 miles of string in a tennis ball”).,,,
    A gene is not in any case the kind of rigidly defined entity one might hope to calculate with. As a functional unit appropriate to current circumstances, it must be cobbled together by the cell according to the needs of the moment. There is no neatly predefined path to follow once the cell has located the “right” half inch or so of string, or once it has done whatever is necessary to bring that locus into proper relation with other chromosomal loci participating in the same “dance”.
    One issue has to do with the fact that there are two strands in the DNA double helix and, starting from any particular point, it is possible to transcibe either of two DNA sequences in either of two directions: “forward” along one strand, or “backward” along the other. This yields two completely different products. One of them is very likely not even a protein-coding RNA, and yet it may still play a vital role in gene expression and in cellular processes more generally.
    And even when the cell would proceed in one particular direction, it must “choose” the exact point in the genetic sequence at which to begin. Different starting points can yield functionally distinct results. “Many studies focusing on single genes have shown that the choice of a specific transcription start site has critical roles during development and cell differentiation, and aberrations in . . . transcription start site use lead to various diseases including cancer, neuropsychiatric disorders, and developmental disorders”.8,,,
    This splicing operation, which is applied to nearly all human RNAs, is performed by the spliceosome, consisting of a few non-protein-coding RNAs and over 300 cooperating proteins, and is hardly less exacting in its requirements than, say, brain surgery.,,,
    The overall picture of gene expression is one of unsurveyable complexity in the service of remarkably effective living processes.,,,
    A decisive problem for the classical view of DNA is that “as cells differentiate and respond to stimuli in the human body, over one million different proteins are likely to be produced from less than 25,000 genes”.30 Functionally, in other words, you might say that we have over a million genes.,,,
    http://www.natureinstitute.org.....nes_29.htm

    Purported Darwinian explanations, (i.e. Darwinian ‘just-so stories”), for trying to explain how this astonishing level of complexity came about are simply nonsensical.

    As David Berlinski noted elsewhere, “…applying Darwinian principles to problems of this level of complexity is like putting a Band-Aid on a wound caused by an atomic weapon. It’s just not going to work.”
    https://www.discovery.org/multimedia/audio/2016/01/david-berlinski-michael-denton-pt-2-darwinian-stalemate/

    Verse:

    Psalm 139:13-14
    For you formed my inward parts; you knitted me together in my mother’s womb. I praise you, for I am fearfully and wonderfully made. Wonderful are your works; my soul knows it very well.

  2. 2
    martin_r says:

    Chromatin, histones, DNA packaging …

    together with DNA proofreading and repair, another undeniable and most obvious proof of engineered cell.

    All rational people (especially with technical education background) can see that. You can not see that, when you are a Darwinist (don’t matter the profession and education)

    If you are a Darwinist, you just have to believe in very absurd things. You have to believe, that natural process solves highly complex engineering problems, and creates things as extremely complex as it gets although there are much simpler solutions (e.g. way shorter DNA, bigger nucleus or no nucleus at all.)

    But no. When you a Darwinist, you have to believe in hard-to-believe things, that instead of keeping things simple, the nature invents an extremely complex DNA packaging system, with lots of unwanted problems, problems which require to invent other supporting tools to keep everything under control and working …

  3. 3
    jerry says:

    To be accurate

    Chromatin First Evolved In Ancient Microbes 1-2 Billion Years Ago, New Research Suggests

    Should be

    Chromatin First Appeared in Ancient Microbes 1-2 Billion Years Ago, New Research Suggests

  4. 4
    relatd says:

    Chromatin and evolved should never appear in the same sentence.

  5. 5
    martin_r says:

    Relatd @4

    a good one :)))

  6. 6
    tjguy says:

    “Since the probability of forming even a single moderate protein by natural processes is too remote to be expected in our universe, the apparently simultaneous appearance of chromatin and eukaryotes is not consistent with an evolutionary explanation.”

    Very true, but since when did that stop them from believing? In the end, the data doesn’t matter because they are going to believe no matter how ridiculous or improbably it might seem. They just ramp up the faith to meet any challenge laid before them.

    When you are drunk on “Darwine” ( a favorite saying of Dave Coppedge @ crev.info), you are willing to believe anything no matter how nonsensical or improbable it may sound.

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