This month’s batch of science tips includes a new twist on a story I have covered previously: Steve Kowalczykowski’s work on DNA repair. Back in 2001, Kowalczykowski and Ron Baskin developed a method for trapping single pieces of DNA and watching a single enzyme, called RecBCD, at work on them. RecBCD’s job is to unwind the DNA double helix so that the two strands can be copied, and Kowalczykowski’s group was able to film this happening in real time. A video of this was posted on the San Francisco Chronicle’s web site in January 2001 and was the most popular download of the month, beating a clip of President Bush’s first inauguration.
Since then Kowalczykowski’s group has exploited the system to learn more about RecBCD, showing that it has two “motors” that run in opposite directions, and that a particular DNA sequence can tell it to throttle back. The group studies DNA repair mechanics in both E. coli bacteria and in humans — when DNA repair goes wrong, it can lead to cancer as harmful DNA damage builds up.
In the latest paper, published this week on Nature’s web site, postdoc Roberto Galletto looks at a different E. coli enzyme, RecA. RecA lines up along DNA strands to form a filament that allows matching DNA to line up alongside and swap over, for DNA repair or copying. It’s like a support that allows the process to happen. For the first time, Galletto could measure how RecA units stick to DNA, form first a cluster, then grow along the strand. Given that baseline, they can look at the rest of the proteins that support the process. In humans, one of those proteins is made by the BRCA2 gene, linked to breast cancer.
It Takes a Village
In other news — Prem Devanbu and colleagues in Computer Science and the Graduate School of Management just got an NSF grant to study how open source software gets written. The characteristic of open source is that the program code is accessible to anyone who wants to work on it, so a large community of programmers can tinker with it. Probably the best known examples are the Linux operating system, Apache web server, and Mozilla and Firefox web browsers. But how do self-assembling teams work on such projects, and do it so efficiently? Devanbu, who specializes in software architecture, thinks that the nature of the teams affects the software, and the software affects the way the programmers work. They’re going to be combing through a lot of bulletin boards and bug reports to find out.
The Benefits of Bumblebees
Sarah Greenleaf, now a postdoc at UC Davis, has published a nice study showing that wild bees make honeybees more efficient at pollinating sunflower crops (and presumably the other fruit crops that rely on insect pollination). Every year, farmers rent beehives to put in their fields to encourage pollination. Greenleaf found that when wild bees were present in the same fields, honeybees moved around from flower to flower more often — apparently because of harassment from both male and female bumblebees. She calculates that the wild bees are worth millions of dollars to the sunflower industry alone. The work was done in Yolo County, around UC Davis, while Greenleaf was a graduate student at Princeton.
UC Davis still has a significant Bee Biology Program, established by the late Harry Laidlaw, who pioneered the artificial insemination of bees and made the study of bee genetics possible. Laidlaw’s work is also said to have inspired this poem by E.B. White.