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Retroviral relplication

Discussion in 'XMRV Research and Replication Studies' started by Emma-Kate, Dec 10, 2009.

  1. Emma-Kate

    Emma-Kate Guest

    Please know at the outset, I am not an expert on this. The information I have used is summarized from my anatomy and physiology books I used in my University days, which I have referenced at the end.

    What, exactly, is a retrovirus?

    Like many people, when I first learned about the research findings regarding XMRV and its potential role in CFS, I immediately wanted to understand a bit about retroviruses. Im naturally a scientifically orientated person; I like not only knowing what something is, but also 'why' it is, and 'how' it works. I know there are others also interested in the 'whats, whys and hows' of things such as this retrovirus, ESPECIALLY when it appears to have suddenly affected us directly. I understand, however, that not everyone considers a textbook good quality bedtime reading, like I occasionally do! And when Im really exhausted, I need something thats accessible to read, either summarized or written in easy to understand terms. I figure that if I benefit from summarizing what I learn about retroviruses for myself, it may also be of benefit to others.

    Part One: DNA to DNA replication (parent to daughter cells sorry guys)

    As I vaguely remember, school taught me that my body is made up of organs, which are in turn made up of millions of cells. Inside every one of my cells is a copy of my individual genetic information, which 'codes' for each of the protein molecules needed to build my specific characteristics and features. This information is held in the centre, or nucleus, of every one of my cells, a fact which is exploited in many crime shows on TV, where the good guys find the bad guys by identifying their bad-guy-DNA in a strand of hair, or drop of blood.
    These cells of mine are replicating constantly, as is the all-important information code held within them called DNA. This cell division process is called mitosis (except in sex cells, but thats a story for another time). Many of us are familiar with the wound up ladder image of DNA, called a double helix, which resides, curled up tight, in the nucleus of a cell. Every time a parent cell replicates, (creates an identical copy of itself by going through the process of cell division), it must also replicate this precious cargo, the DNA. To do this, the DNA unwinds, and begins to separate at one end of the ladder, right down the middle of each 'rung, so we now have two 'half-ladders at one end of the unwound DNA strand. Each of these half-rungs along the length of separated DNA is a molecule. These individual molecules are called a nucleotides'. Both of these half-ladders of nucleotides are now ready to act as templates for replication. An enzyme, 'polymerase', (a blue-collar worker), speeds in wearing his sweat bands, and starts frantically matching new, individual, nucleotides to the original, exposed nucleotides of each one of the 'half-ladders of original DNA, which leads to the rebuilding of TWO whole (and, of course, identical) ladders of DNA once again . Eventually, these ladders coil up again into two strands, and link at the centre, forming a pretty standard X-shape. We can now call this pretty standard X-shape a chromosome. When the parent cell divides into two, it pulls apart our standard X-shaped chromosome, so that each daughter cell ends up with one ladder of DNA, at which point the process begins again. But this is not the only form of replication that occurs.

    Part Two: DNA to RNA replication (Protein synthesis)

    As mentioned previously, my individual DNA stores the information on how to build each specific protein molecule my cells need in order to function, and on a grander scale, these proteins dictate my characteristics. The problem is my DNA never leaves the nucleus of a cell. Therefore, I need something to go on an adventure into the cell nucleus, to get the information off the DNA and translate it into protein molecules. RNA is up to the task. During a process called transcription, RNA builds up a copy of the DNA strand inside the nucleus, in a similar manner as when DNA replicated itself. The DNA ladder uncoils and splits down the centre of each rung for the length requiring. Once the RNA has finished making a copy of the DNA, it gracefully exits the nucleus. Once the RNA is outside the nucleus, it begins the process called translation, where the RNA strand is literally translated into the specific proteins molecules that underlie all cellular activities. So what does this have to do with a virus?

    Part Three: Virus and retrovirus replication

    Viruses are super tiny obligate parasites, meaning that they require a living host cell in which to replicate. Aside from being so small, they are also rather simple in their structure. A virus is a strand of either DNA or RNA, wrapped up in a protective protein coat, and some also have a fatty envelope which provides added protection when they are outside of host cells. Unlike cell division, viruses replicate by using the mechanisms available in a host cell. So, a virus comes up to one of my healthy, living cells and enters through the cell wall, or injects its genetic material into the cell (as is the case for bacteria cells). The virus then manipulates the replication machinery of the my host cell, if its genetic code is DNA, it enters the nucleus of my cell and makes copies of itself in the same way my own DNA replicates, as described in part one. (If its genetic code is RNA, it replicates outside of the nucleus, and may or may not create proteins). When the virus completes its replication, it exits the cell by bursting the cell membrane and killing the cell.
    The retrovirus is an RNA virus, however, instead of creating copies of its RNA in my host cell, it uses an enzyme called reverse transcriptase to produce DNA. (If you remember in part two, this process usually works the other way, and my DNA code is copied by the RNA and used to produce protein molecules). This DNA copy of the virus is then incorporated into my DNA genome, residing in the nucleus of my cell, and replicates, along with the rest of my genome, during each cell division process.

    It is suggested that up to 8% of the human genome has been acquired over the generations through retroviruses, however much of this genetic information does not appear to code for anything and is thus called junk-DNA.

    I hope that some of this is helpful, and gives a little insight to the processes going on at a molecular level, for those interested. If there is anything you wish to add, change or remove, let me know, or if you want further information, contact me for a list of references.

    Gallo, R, C., (1991). Virus hunting AIDS, cancer and the human retrovirus: A story of scientific discovery. USA: BasicBooks.

    Marieb, E., (2001). Anatomy and physiology (5th ed.). pp 94 109. USA: Benjamin-Cummings pub co.

    If you want to get in touch with me at aenimus_@hotmail.com, or send me a message through facebook
  2. Eric Johnson from I&I

    Eric Johnson from I&I Senior Member

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    Nice. However, retroviruses (and some other enveloped viruses) bud serenely from the host cell surface; they consider it tasteless to burst the cell (or even bring up such a subject publicly), and would be scandalized by your lumping them in with the rest.

    You might like this free book edited in part by Coffin:
    http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=rv
  3. fresh_eyes

    fresh_eyes happy to be here

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    mountains of north carolina
    An aristocrat among viruses!

    Well, I don't like to brag, but yes, I do have one of the most *tasteful* viruses. :eek:

    ps Thanks for posting your research, Emma-Kate - that's great.
  4. Emma-Kate

    Emma-Kate Guest

    Thanks Eric and yes I was aware of that however without having added drawings and in the interest of keeping it simple I must have avoided that description. I shall make the change; thank-you! I did only do this for the benefit of my brother, mother, husband and I and posted it here at the request of a friend plus I am very limited in my understanding (my usual playground is cosmology and physics). Have a lovely day.
  5. fresh_eyes

    fresh_eyes happy to be here

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    Forgot to say - and welcome to the boards! :)
  6. Eric Johnson from I&I

    Eric Johnson from I&I Senior Member

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    Physics, whoa. Hat's off to you. One thing that makes molecular bio and biochem a little simpler, is to realize explicitly that electric force is very, very nearly the only force that acts. Youre probably alert to that, but maybe it will be news to some reader. Medical biology is not terribly demanding, really, compared to some subjects which are rather beyond me.

    A nice day to you and your family too.
  7. flybro

    flybro Senior Member

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    pluto
    Thanks EmmaK.

    Much appreciated, I've read it thrice now, and some of it are starting to stick.

    Hugs
  8. Emma-Kate

    Emma-Kate Guest

    Hey flybro, I have been wondering how you are but I am not online much as a bit unwell. Hope your doing ok, my dear, thanks for sending me here. ek
  9. flybro

    flybro Senior Member

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    pluto
    It's a great place Emma, I think you'll really enjoy it, plus your an asset.

    I'm glad your here, and I think you'll be right at home.
  10. Martlet

    Martlet Senior Member

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    Near St Louis, MO
    I'd like to echo the welcome. I think you'll find that this is a great place for support, as well as for information.
  11. Emma-Kate

    Emma-Kate Guest

  12. shannah

    shannah Senior Member

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    XMRV Replication

    So once inside you, do the different retroviruses vary in the paths they take to replicate?

    For instance, Judy Mikovits in the Nevada Newsmakers interview says:

    "these viruses live and divide and grow in the lymphocytes: the immune response cells, the B and the T cells"

    so it makes sense that we don't want to stimulate these cells for now. Yet when looking at some of the holistic therapies for HIV, they use alternatives that do stimulate these very same cells.

    This leads me to believe that the two retroviruses may behave differently once inside the host. Do we know how HIV replicates? Do we know any differences that might explain why it is beneficial to boost the same cells when dealing with one retrovirus yet try to inhibit these cells when dealing with another?
  13. _Kim_

    _Kim_ Guest

    Shannah, Nancy Klimas does a nice job of explaining XMRV replication in Section 6 of the lecture that she gave last month.

    This part of her lecture is worth watching (very cool animations), but there is also a transcription on Cort's website. Scroll down to the bottom of this page to find Section 6.
  14. guest

    guest Guest

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    Thanks for the link, Kim. I have a question. Dr Klimas says:

    "Now of the negative, these 33 negatives, they went on and looked in other ways. And they found 19 of those had antibody in their plasma, so that was more than half of those negatives. But this is the big number: 30 of the negatives had virus they could identify by taking the serum of those cells, the serum from the plasma, and infecting a cell line and then growing the virus in that cell line. So they could transfer from the plasma, virus to the cell line."

    I dont understand what they did with the 30 negatives, where they could find the virus in the serum. They took the serum and put it next to a cell line and then the cell line got infected?

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