Department of Microbiology, New York University School of Medicine, New York, New York, USA.
PLoS Genet. 2010 Jan 22;6(1):e1000824. doi: 10.1371/journal.pgen.1000824.
Prions are self-propagating protein conformations. Transmission of the prion state between non-identical proteins, e.g. between homologous proteins from different species, is frequently inefficient. Transmission barriers are attributed to sequence differences in prion proteins, but their underlying mechanisms are not clear. Here we use a yeast Rnq1/[PIN(+)]-based experimental system to explore the nature of transmission barriers. [PIN(+)], the prion form of Rnq1, is common in wild and laboratory yeast strains, where it facilitates the appearance of other prions. Rnq1's prion domain carries four discrete QN-rich regions. We start by showing that Rnq1 encompasses multiple prion determinants that can independently drive amyloid formation in vitro and transmit the [PIN(+)] prion state in vivo. Subsequent analysis of [PIN(+)] transmission between Rnq1 fragments with different sets of prion determinants established that (i) one common QN-rich region is required and usually sufficient for the transmission; (ii) despite identical sequences of the common QNs, such transmissions are impeded by barriers of different strength. Existence of transmission barriers in the absence of amino acid mismatches in transmitting regions indicates that in complex prion domains multiple prion determinants act cooperatively to attain the final prion conformation, and reveals transmission barriers determined by this cooperative fold.
朊病毒是自我传播的蛋白质构象。朊病毒状态在非同源蛋白质之间的传递，例如不同物种同源蛋白质之间的传递，通常效率低下。传递障碍归因于朊病毒蛋白中的序列差异，但它们的潜在机制尚不清楚。在这里，我们使用基于酵母 Rnq1/[PIN(+)]的实验系统来探索传递障碍的性质。[PIN(+)], Rnq1 的朊病毒形式，在野生和实验室酵母菌株中很常见，在这些菌株中，它促进了其他朊病毒的出现。Rnq1 的朊病毒结构域携带四个离散的 QN 丰富区域。我们首先表明，Rnq1 包含多个朊病毒决定簇，这些决定簇可以独立地在体外驱动淀粉样纤维形成，并在体内传递[PIN(+)]朊病毒状态。随后对具有不同朊病毒决定簇的 Rnq1 片段之间的[PIN(+)]传递进行分析，结果表明：（i）一个共同的 QN 丰富区域是必需的，通常足以进行传递；（ii）尽管共同 QN 的序列相同，但这种传递受到不同强度的障碍的阻碍。在传递区域没有氨基酸错配的情况下存在传递障碍表明，在复杂的朊病毒结构域中，多个朊病毒决定簇协同作用以达到最终的朊病毒构象，并揭示了由这种协同折叠决定的传递障碍。
