The holoenzyme formed by RNA polymerase II (RNAPII) and the Mediator complex is the target of transcriptional regulators in vivo. A three-dimensional structure of the yeast holoenzyme has been generated from electron microscopic images of single holoenzyme particles. Extensive changes in Mediator conformation required for interaction with RNAPII have been modeled by correlating the polymerase-bound and free Mediator structures. Determination of the precise orientation of the RNAPII in the holoenzyme indicates that Mediator contacts are centered on the RNAPII Rpb3/Rpb11 heterodimer, the eukaryotic homolog of the alpha(2) homodimer involved in transcription regulation in prokaryotes. Implications for the possible mechanism of transcription regulation by Mediator are discussed.

Biochemical evidence suggesting that the predominant form of Mediator in the yeast Saccharomyces cerevisiae might be one in which the complex is associated with RNA polymerase II to form a holoenzyme has led to the proposition of a holoenzyme-based model for transcription initiation. We report that polymerasefree Mediator, isolated early on during a whole-cell extract fractionation protocol, is in fact the most abundant form of the Mediator complex. The existence of free Mediator would make possible independent recruitment of Mediator and RNA polymerase II to the preinitiation complex. This is in agreement with reports from in vivo studies of time and spatial independence of Mediator and RNA polymerase II promoter interaction, with current models of preinitiation complex structure in which promoter DNA upstream of the transcription start site is positioned between Mediator and polymerase, and with the proposed role of Mediator as the major component of the Scaffold complex involved in transcription reinitiation.

This study investigated the phonological preparation unit when planning spoken words with native Chinese speakers who speak English as a Second Language (ESLs). In Experiment 1, native Chinese speakers named pictures in Chinese, and the names shared the same onset, same rhyme, or had nothing systematically in common. No onset effect was shown, suggesting that native Chinese speakers did not use onset as their preparation unit. There was a rhyme interference effect, probably due to lexical competition. In Experiment 2, the same task was conducted in English among Chinese ESLs and native English speakers. Native speakers showed onset facilitation whereas ESLs did not show such an effect until Block 3. ESLs’ phonological preparation unit is likely to be influenced by their native language but with repetition they are able to attend to sub-syllabic units. Both groups showed rhyme interference, possibly as a result of joint lexical and phonological competition.

The present study investigated the representation and processing of segmental and tonal information in visual Chinese word recognition in native and non‐native Chinese readers. Two experiments using homophone judgement paradigm were conducted. When judging two Chinese characters (Experiment 1), both groups showed difficulties when the segmental but not tonal information was shared (i.e., S+T− condition), with stronger interference for non‐native readers. When judging a Pinyin and a Chinese character (Experiment 2), non‐native readers' S+T− disadvantage was significantly reduced. Finally, when their L1s share the Latin alphabets with Pinyin, the participants showed stronger segmental reliance compared with the native readers. These findings suggest that while both native and non‐native readers rely more on segmental information in Chinese visual word recognition, this reliance is stronger among non‐native readers. Furthermore, the alphabetic nature of the Pinyin orthography may help non‐native readers' phonological representation and processing in a nonalphabetic writing system.

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