Interactome of Site-Specifically Acetylated Linker Histone H1.

Linker histone H1 plays a key role in chromatin organization and maintenance, yet our knowledge of the regulation of H1 functions by post-translational modifications is rather limited. In this study, we report on the generation of site-specifically mono- and di-acetylated linker histone H1.2 by genetic code expansion. We used these modified histones to identify and characterize the acetylation-dependent cellular interactome of H1.2 by affinity purification mass spectrometry and show that site-specific acetylation results in overlapping but distinct groups of interacting partners. Among these, we find multiple translational initiation factors and transcriptional regulators such as the NAD+-dependent deacetylase SIRT1, which we demonstrate to act on acetylated H1.2. Taken together, our data suggest that site-specific acetylation of H1.2 plays a role in modulating protein-protein interactions.

Multiple aspects related to self-awareness and the awareness of others: an electroencephalography study.

The effect of possessive pronouns on the encoding of pronoun-noun associations (e.g., my garden) was investigated using the electroencephalography (EEG). Following an alphabetical, semantic and a contextual encoding instruction depth of noun processing was varied within three separate experiments in order to manipulate the grade of awareness related to verbal information processing. Only for the semantic encoding task (lexical decision) response time was significantly longer for nouns associated with the pronoun "mein" (German for "my") than for nouns associated with the pronoun "ein" (German for "a") although pronouns were not to be consciously processed at all. Following recognition tests related to nouns (without their previously associated pronouns) revealed no significant differences related to the number of correctly identified repeated nouns (hits) depending on the kind of previously associated pronoun. The analysis of neurophysiological data revealed a time range between about 250 ms and 400 ms after stimulus onset within which significant pronoun x electrode interactions occurred. No interaction with depth of word processing was found. Overlaid EEG curves, t maps and low resolution brain electromagnetic tomography (LORETA) demonstrate that in this time range "mein" and "sein" associated conditions elicit similar brain activity, both more negative, compared to the "ein" associated condition over occipital electrodes. On the other hand, at left temporal sites the "mein" condition elicited more negative potentials than both other conditions. It is interpreted that EEG recordings reveal two relevant areas, which are sensitive to the concept of a person (as represented by a personal pronoun) between about 250 ms and 400 ms after stimulus onset. One area is located in the occipital region and can distinguish between personal engagement and a neutral condition and the other area is located in the temporal region and is able to distinguish between oneself and somebody else. Together with our previous MEG results (Walla et al. in Neuropsychologia 45:796-809, 2007) we want to combine the inferences in the frame of the "multiple aspects" hypothesis related to research on self-awareness and the awareness of others.

Self-awareness and the subconscious effect of personal pronouns on word encoding: a magnetoencephalography (MEG) study.

The effect of personal pronouns such as "ein" (German for "a"), "mein" (German for "my") and "sein" (German for "his") on the processing of associated nouns was investigated using MEG. Three different encoding strategies were provided in order to vary the level of consciousness involved in verbal information processing. A shallow (alphabetic), a deep (semantic) and a very deep (contextual) encoding instruction related to visual word presentation were given to all study participants. After the encoding of pronoun-noun pairs, recognition performances of nouns only were tested. The number of correctly recognized nouns previously associated with "sein" was significantly lower than the number of correctly recognized nouns previously associated with "ein" in the shallow encoding condition. The same trend was found for "mein" associated nouns which were also less accurately recognized compared to "ein" associated nouns. Magnetic field distributions recorded during the encoding phases revealed two significant effects, one between about 200 and 400ms after stimulus onset and the other between about 500 and 800ms. The earlier effect was found over occipito-parietal sensors, whereas the later effect occurred over left frontal sensors. Within both time ranges, brain activation varied significantly as a function of associated pronoun independent of depth of word processing. In the respective areas of both time ranges, conditions including personal pronouns ("mein" and "sein") showed higher magnetic field components compared to the control condition of no personal pronouns ("ein"). Evidence is shown that early stage processing is able to distinguish between no personal and personal information, whereas later stage processing is able to distinguish between information related to oneself and to another person (self and non-self). Along with other previous reports our MEG findings support the notion that particular human brain functions involved in processing neurophysiological correlates of self and non-self can be identified.