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Adam Pavlícek

Publications and source records attributed to Adam Pavlícek.

8 recordsLinked to original sources
PubMed2003

A unification of mosaic structures in the human genome.

The human genome is a mosaic structure on many levels: there exist cytogenetic bands, GC composition bands (isochores) and clusters of broadly expressed genes. How might these inter-relate? It has been proposed that to optimize gene regulation, housekeeping genes should concentrate on transcriptionally competent chromosomal domains. Prior evidence suggests that regions of high GC and R bands are associated with such domains. Here we report that broadly expressed genes cluster in regions of high GC, and in R and lightest Giemsa bands. This is not only a confirmation of the adaptive hypothesis, but is also the first direct systematic evidence of a general interdependence of expression patterns with base composition and chromosome structure.

Azure Stains↗
PubMed2002

Length distribution of long interspersed nucleotide elements (LINEs) and processed pseudogenes of human endogenous retroviruses: implications for retrotransposition and pseudogene detection.

Deciphering the human genome includes reliable identification and structural characterization of individual retrotransposon elements. The most active group of autonomous transposable elements, the long interspersed nuclear elements (LINE), transpose themselves as well as other RNAs, including those of human endogenous retroviruses (HERV). During this transposition, however, the LINE-encoded reverse transcriptase (RT) often abortively dissociates from the RNA template, leaving a prematurely terminated, 5' truncated copy. We have analyzed the length distributions of LINEs and of processed pseudogenes derived from HERV-W. As expected, we have found that the majority of 5' truncated LINEs and HERV-W processed pseudogenes show a prevalence of very short elements terminated close to the 3' end. On the other hand, the number of complete elements is far above the expectation. The characteristic distribution in both cases indicates two important conclusions: (i) dissociation of LINE RT from the template cannot be fully explained by low processivity of RT modelled as a stochastic, Poisson-type process. (ii) Currently cited numbers of pseudogenes within the human genome are underestimated, since a large percentage of pseudogenes are terminated in the 3' untranslated region and remain undetectable in translated homology searches of protein databases against the human genome.

Endogenous Retroviruses↗
PubMed2002

A compact view of isochores in the draft human genome sequence.

Prior to genome sequencing, information on base composition (GC level) and its variation in mammalian genomes could be obtained using density gradient ultracentrifugation. Analyses using this approach led to the conclusion that mammalian genomes are organized into mosaics of fairly homogeneous regions, called isochores. We present an initial compositional overview of the chromosomes of the recently available draft human genome sequence, in the form of color-coded moving window plots and corresponding GC level histograms. Results obtained from the draft human genome sequence agree well with those obtained or deduced earlier from CsCl experiments. The draft sequence now permits the visualization of the mosaic organization of the human genome at the DNA sequence level.

Base Composition↗
PubMed2002

HERVd: database of human endogenous retroviruses.

The human endogenous retroviruses database (HERVd) is maintained at the Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, and is accessible via the World Wide Web at http://herv.img.cas.cz. The HERVd provides complex information on and analysis of retroviral elements found in the human genome. It can be used for searches of individual HERV families, identification of HERV parts, graphical output of HERV structures, comparison of HERVs and identification of retrovirus integration sites.

Animals↗
PubMed2002

Processed pseudogenes of human endogenous retroviruses generated by LINEs: their integration, stability, and distribution.

We report here the presence of numerous processed pseudogenes derived from the W family of endogenous retroviruses in the human genome. These pseudogenes are structurally colinear with the retroviral mRNA followed by a poly(A) tail. Our analysis of insertion sites of HERV-W processed pseudogenes shows a strong preference for the insertion motif of long interspersed nuclear element (LINE) retrotransposons. The genomic distribution, stability during evolution, and frequent truncations at the 5' end resemble those of the pseudogenes generated by LINEs. We therefore suggest that HERV-W processed pseudogenes arose by multiple and independent LINE-mediated retrotransposition of retroviral mRNA. These data document that the majority of HERV-W copies are actually nontranscribed promoterless pseudogenes. The current search for HERV-Ws associated with several human diseases should concentrate on a small subset of transcriptionally competent elements.

Base Sequence↗