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This Week in Cell: Apr 15, 2009

Chromatin-associated proteins and histone modifications can be maintained through many rounds of transcription, but it wasn't known whether these complexes stay bound. Scientists at Harvard examined the PRC1-class Polycomb group protein complexes in an in vitro transcription experiment and found that Polycomb complexes remain bound to replicated templates. "Retention of Polycomb proteins through DNA replication may contribute to maintenance of transcriptional silencing through cell division," they say in the abstract.

Researchers looked at how unconventional polyubiquitin chains linked through K6, K11, K27, K29, or K33 participate in protein degradation through the ubiquitin system. They profiled both the entire yeast proteome and ubiquitinated proteins in wild-type and ubiquitin K11R mutant strains using mass spec and identified K11 linkage-specific substrates to be involved in endoplasmic reticulum-associated degradation, suggesting that "unconventional polyubiquitin chains are critical" in the ubiquitin-proteasome system.

In a study led by Susan Lindquist and Simon Alberti at the Whitehead Institute, researchers performed bioinformatic analysis on the S. cerevisiae proteome to look for prion proteins and identified 100 candidates. They found that 19 of them could form prions and that at least one, Mot3, "produces a bona fide prion in its natural context that increases population-level phenotypic heterogeneity."

Italian researchers used synthetic biology to test reverse-engineered systems biology networks. After building a five-gene synthetic network, they measured time series and steady-state expression data after multiple perturbations and then used this data to compare the effectiveness of sys bio modeling techniques. Reverse engineering based on differential equations and Bayesian networks correctly inferred regulatory interactions from the experimental data, they say in the abstract.

The Scan

Pig Organ Transplants Considered

The Wall Street Journal reports that the US Food and Drug Administration may soon allow clinical trials that involve transplanting pig organs into humans.

'Poo-Bank' Proposal

Harvard Medical School researchers suggest people should bank stool samples when they are young to transplant when they later develop age-related diseases.

Spurred to Develop Again

New Scientist reports that researchers may have uncovered why about 60 percent of in vitro fertilization embryos stop developing.

Science Papers Examine Breast Milk Cell Populations, Cerebral Cortex Cellular Diversity, Micronesia Population History

In Science this week: unique cell populations found within breast milk, 100 transcriptionally distinct cell populations uncovered in the cerebral cortex, and more.