There are several simple problems that are often at the root of communication failures. Sometimes, this may be because the speaker is not thinking clearly. Sometimes this might be because the speaker really does not understand what they are talking about at all. Sometimes, it might even be that the speaker knows what they are talking about too well. In his recent book, The Sense of Style: The Thinking Person’s Guide to Writing in the 21st Century, Harvard Psychologist, Steven Pinker, argues that the curse of knowledge is often to blame. Check out this Inc. article by Glenn Leibowitz on the topic.
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A graphic and a short film on the Wuhan Coronavirus.
The reproduction number is a valuable piece of information that enables epidemiologists to predict how rapidly a virus (or other infectious organism) will spread within a population. For comparison, Measles has a reproduction number of 12-18, which is extraordinarily high, the 1918 influenza that was responsible for infecting some 500 million people worldwide had a reproduction number of 2-3.
The reproduction number tells us nothing about the lethality of the virus, but it does tell us how quickly we can expect it to spread.
Here is a short film showing the impact that the Wuhan virus is having in one small community in China.
This week in my Molecular class we discussed the role of sigma (σ) factors in regulating transcription. Sigma factors are proteins which bind to the DNA-Dependent RNA polymerase and mediate that enzyme’s binding to the promoters of prokaryotic genes. In this way, we can consider the core polymerase enzyme to be agnostic to which genes are transcribed, it is only the mediation of the sigma factor that guides the polymerase to one gene or another.
Under resting conditions, σ70 is expressed highly and guides the polymerase to constitutively express ‘normal’, housekeeping genes. However, under conditions of stress, such as heat shock, another sigma factor, σ24, becomes active, leading to the transcription (and subsequent translation) of a third factor, σ32. This third sigma factor then leads the polymerase to translate a number of heat shock response proteins such as chaparones, which help prevent protein denaturation and aggregation.
The question is, how does σ24 know when to become active and initiate this heat shock cascade?
Before answering this, we should ask ourselves what to expect.
How can a cell respond to heat shock before the heat shock proteins are made? The answer must be that somehow the heat shock itself leads to a difference in the sigma factors being utilized. I speculated in class that one possible mechanism would be that either the polymerase or σ24 might partially denature in a way that their association was favored over that of the polymerase and σ70.
Although that could work, it turns out not to be the case.
Boldrin et al. examine this question in the bacteria Mycobacterium tuberculosis and suggest that an anti-sigma factor, regulator of sigma E factor A (RseA), binds σ24 (which they call σE – however, I will continue calling it σ24 for consistency) and sequesters it under resting conditions. They continue, “[i]f [RseA] acted as a σ24-specific anti-sigma factor, we would expect to detect an upregulation of those genes whose expression is regulated by σ24 when [RseA] is absent.” One such gene regulated by σ24 is sigB.
To demonstrate that σ24 does regulate sigB, cells missing σ24 were generated. Indeed, the expression of sigB was repressed about 10 times in these cells compared to the wild type (Figure 4). Similarly, when RseA was overexpressed, sigB was also repressed(Figure 5). Genes not regulated by σ24 were unaffected by the deletion of σ24 or the overexpression of RseA (data not shown)
Taken together these data indicate that the absence of RseA specifically increases the activity of σ24.
De Las Peñas et al. confirm that RseA is predicted to be an inner membrane protein, and the purified cytoplasmic domain binds to and inhibits σ24.
Of course the rabbit hole continues to deepen as we ask how RseA knows to release . It turns out that (cellular) envelope stress promotes RseA degradation, which occurs by a proteolytic cascade initiated by DegS, but that’s as far as we’ll go here. I hope this helps!
Assessing the role of Rv1222 (RseA) as an anti-sigma factor of the Mycobacterium tuberculosis extracytoplasmic sigma factor SigE Francesca Boldrin, Laura Cioetto Mazzabò, Saber Anoosheh, Giorgio Palù, Luc Gaudreau, Riccardo Manganelli & Roberta Provvedi Scientific Reports volume 9, Article number: 4513 (2019)
The σE‐mediated response to extracytoplasmic stress in Escherichia coli is transduced by RseA and RseB, two negative regulators of σE Alejandro De Las Peñas, Lynn Connolly, and Carol A. Gross 31 October 2003
The Single Extracytoplasmic-Function Sigma Factor of Xylella fastidiosa Is Involved in the Heat Shock Response and Presents an Unusual Regulatory Mechanism José F. da Silva Neto, Tie Koide, Suely L. Gomes, Marilis V. Marques Journal of Bacteriology Dec 2006, 189 (2) 551-560
I didn’t know the song Ocean, by the Velvet Underground, despite owning Unloaded for years, until I hear a cover version by MGMT off their Late Night Tales album.
I wasn’t very impressed. in fact, as the song neared its end, I was struck by the realization that it had a bizarre ripoff of Alive and Kicking‘s signature riff. I was a little angry that MGMT had pulled off this larceny and was determined to listen more closely to see if I was right.
Unfortunately, it was as if the song didn’t exist – I kept googling “MGMT ocean” to find a youtube version to play side-by-side against the Simple Minds’ song, but I kept coming up short. Until I added the album name, ‘Late Night Tales‘ to my search and found the Underground version. And then I was stuck.
Alive and Kicking came out in 1985, Ocean came out on the Velvet Underground’s VU album the same year. So, neither was a copy of the other, just two bands hitting similar riffs at the same time. However, Ocean had been recorded for MGM studio years earlier, in 1969, and was simply shelved until its release on VU.
Except that there was another version re-recorded by the Underground, but released on Lou Reed’s eponymous album in 1972. So it is possible that Simple Minds had heard this and was influenced by it.
Or maybe I’m just hearing things that aren’t there.
And if I’m really interested in hearing an ocean song, it’s probably this one:
It’s tempting to think of genes as simply a series of nucleotides beginning with a START codon and ending with one of the three STOP codons. However, there are a number of additional regulatory elements that must be present in order for a gene to be transcribed and translated appropriately.
Transcription is regulated by signals for the DNA-dependent RNA Polymerase ( or simply ‘RNA Polymerase’) to attach and detatch from the DNA in the nucleus.
The attachment point is known as the promoter, and ‘Initiation’ of transcription is characterized by the recruitment of the RNA polymerase to the DNA upstream of the coding sequence. Polymerase engagement unwinds the DNA allowing for recruitment of ribonucleotides and the start of RNA synthesis (Elongation). There may be a number of false starts until a sufficiently long RNA is made to stabilize the enzyme, and even after elongation begins, it may stall and restart until the polymerase reaches a termination signal. There are a number of different kinds of termination signals, but they all occur downstream of the stop codon and serve to disengage the polymerase from the DNA (Termination) so that it is free to recycle back to the promoter.
There are some key differences between the ways that prokaryotes and eukaryotes perform these operations, but all the above elements occur in each system. The key to understanding this clearly is that transcription must occur before translation, and therefore, the transcribed region must have all the translated region within it. This sounds obvious, but can be helpful in order to envision the gene correctly as a physical object.
Imagine that you are a scientist interested in cloning gene A. You’ve just amplified the entire gene A including some flanking sequence by PCR and run the resulting amplicon onto a 2% gel with a 100 bp ladder. See the results in Figure 1.
Happy with your result, you clone the DNA into a cloning vector, pCR2.1 where you can make up tons of DNA to work with. These cloning vectors are great for making lots of DNA, but they do not express any of the genes as proteins (i.e. the DNA is replicated, but not transcribed and translated.) Because you do want to express protein, you need to subclone your gene from the cloning vector into an expression vector. To complicate matters, the gene needs to go into the expression vector with the promoter upstream of the gene and the poly A signal downstream of the gene (See Figure 2). The promoter is the location that the RNA polymerase binds to transcribe the gene, the polyA site is what signals the polymerase to add a polyA tail to the mRNA.
In order to clone your gene into the expression vector, you decide to determine the direction that your gene has inserted into pCR2.1. To do this, you take advantage of the fact that there is a NotI site off-center in the insert and also one in the plasmid (See Figure 3). Gene A is just under 900bp long in total, the Not I site is located at position 800bp.
You cut the plasmid with NotI expecting either an ~800bp band or a ~100bp band depending upon the orientation of the insert. The results of your digest are seen in figure 4, leading you to believe that your insert is in the direction seen in figure 5.
In order to subclone from the cloning vector into the expression vector (figure 6), you cut the gene out of pCR2.1 with SpeI and NsiI and isolate the ~900 bp fragment. The same two enzymes can be used to open the expression vector and isolate the linear plasmid. The two fragments can then be combined in the presence of DNA ligase to complete the subcloning.
What was it that made Alien more gripping, more terrifying, less …known than Covenant?
Was it character development?
Perhaps something about the grit of the Nostromo?
Maybe working with a much more limited budget spurred creativity in response to necessity.
Or maybe it’s just that we do our most creative works when we’re young?
Quite simply, at least in the sciences, if you haven’t contributed a great work to society by age 40, the likelihood of doing so is about to quickly drop. By 60, it’s vanishingly small (first figure).
There’s some adjustment allowed for those who have earned their terminal degree later in life, possibly accounting for many of the late achievers above (second figure).
Artists and writers reach their peaks at about the same time in their lives according to an article by Christopher Ingraham of the Washington Post.
Sir Ridley Scott fits the pattern perfectly. Born in 1937, he was 42 when he made the original Alien in 1979. Three years later he released his other opus, Blade Runner, and although he continued to make greatly successful films throughout his long career, few have been as widely regarded as groundbreaking.
Screenwriter, Dan O’Bannon was 33 when he wrote the script for Alien; H.R. Giger was also 40 at the time he was producing the art design for the film. For completeness sake, Philip K Dick was 40 when he wrote Do Androids Dream of Electric Sheep, the novel that later became Blade Runner.
So, perhaps it should come as no surprise that Scott’s return (now at 79 years old) to the franchise with Prometheus in 2012 and Covenant in 2017 was unlikely to achieve the success of the original.
Prometheus and Covenant represent prequels meant to explore the origins of the aliens – and – why not explore the origins of all humanoid life? They also continue the cautionary tale of AI being the end of us which started in the original, took a break in the first sequel (apparently, James Cameron doesn’t share Scott’s feelings about technology) only to return with Fassbender’s David & Walter.
Prometheus begins with allusions to a prior race seeding the galaxy (?) with its DNA – a difficult pill to swallow as it suggests an origin of humanity unique from the other life on Earth. This may be fascinating as a science fiction premise, but completely absurd biologically. Nevertheless, the connection to Prometheus, the rogue Titan, makes sense thematically.
Similarly, Covenant begins with speculation about creation as the android, David, awakens to the world in a room that makes the monolith room from 2001 look cluttered with junk. “So, you made me. But who made you?” Deep thoughts, David. Already, David moved from infant to irritating college freshman just out of the first class of intro to philosophy. You can see Weyland already annoyed by his creation, “Play the Piano, David.”
David doesn’t appear scarred in the moment, but obviously, it’s had some effect. Many years later David’s still hung up on being creative and has filled his whole playhouse with sculptures, sketches all over the walls of his creations like a psychotic Leonardo DaVinci, and undoubtedly some angst-ridden poetry amongst his piles of scrolls.
But this is ultimately a film about these two androids – ‘artificial persons,’ as Bishop, the artificial person from Aliens, prefers.
David, the original, is all too human: creative, self-serving, and cruel. Walter, the modern model, is none of these. Walter tells us that David’s individualism scared the humans in charge and they made modifications to prevent these characteristics from emerging in newer models.
“You have symphonies inside you,” David tells Walter while teaching him to play a flute. He can play, but not compose. The whole scene reminds us of Scott’s other masterpiece, BladeRunner, as Rutger Hauer telling Harrison Ford of seeing “… things you people wouldn’t believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain.”
Here we have the director’s real passion. The nature of life. The futility of mortality. We’re even given a recitation of Shelley’s Ozymandias. Only Gather Ye Rosebuds could be plainer in giving us insight into Sir Scott’s mind. After all, are we not looking out over a plain that could easily be the crumbled remains of the King of Kings’ empire? Could it be that Scott is recognizing his age and taking time to reflect on the meaning of it all? Or, is this just an eternal question that he has pondered all his life? The Ozymandias scene is one of the best in the film, despite the similarity to his other work.
“We are food for worms, lads.”
Another improvement is that Walter can heal himself immediately, while David either cannot, or heals slowly, like the humans he is designed to replicate. We’re shown this ability early and it’s obvious later, when it should be much subtler.
As a fan of the franchise, I was going to see this film no matter what, but I also had to come home and watch Alien and Aliens over the next two nights to remember why.