Azokh caves excavations 2002-2006: Middle-Upper palaeolithic transition in Nagorno-Karabagh

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Repair of gamma ray-induced S1 nuclease hypersensitive sites in yeast depends of homologous mitotic recombination and a RAD18-dependent function.

Repair under non-growth conditions of DNA double-strand breaks (DSB) and chromatin sites sensitive to S1 endonuclease (SSS) induced by 60Cobalt-gamma rays were monitored in repair-competent and deficient strains of Saccharomyces cerevisiae by pulsed field gel-electrophoresis. In stationary-phase cells of a repair-competent RAD diploid, and an excision-deficient rad3-2 diploid, SSS are repaired as efficiently as DSB, whereas in a repair-competent RAD haploid, and a rad 50-1 diploid, neither SSS nor DSB are repaired. The rad18-2 diploid repairs DSB well but is defective in SSS repair. Obviously, SSS repair in yeast chromatin, like DSB repair, depends on recombination, but unlike DSB repair depends additionally on RAD18 function

Taphonomy of DNA in rodents.

International audienceMicromammals, particularly rodents, are important paleoenvironmental indicators and their investigation has the potential to deliver a large amount of invaluable information for the interpretation of archeological sites and past environments. Data from paleogenetic and paleogenomic analyses of this important resource could contribute substantially to these interpretations. Most rodent remains, however, originate from accumulations through predators, such as pellets of raptors. In modern pellets, we could show that the passage of rodents through the digestive tract heavily damages DNA in their bones and teeth although the extent of DNA damage depends on the location of the remains in the stomach of the predator and the duration they are subject to the attack of the gastric juices. Thus, a minute portion of DNA can be rather well preserved. It is likely that it is this portion that is prone to long-term preservation since we could show DNA to be preserved in rodent remains from the El Harhoura2 cave in Morocco in levels dated to ca. 6,000 and 44,000 years. We also performed experiments of monitored taphonomy and analyzed DNA degradation and the transformation of the microbiome in bones of mice buried for different time intervals covering a period of 2 years. These experiments shed light on the processes through which biological specimens turn into environmental specimens

Taphonomy of DNA in rodents.

International audienceMicromammals, particularly rodents, are important paleoenvironmental indicators and their investigation has the potential to deliver a large amount of invaluable information for the interpretation of archeological sites and past environments. Data from paleogenetic and paleogenomic analyses of this important resource could contribute substantially to these interpretations. Most rodent remains, however, originate from accumulations through predators, such as pellets of raptors. In modern pellets, we could show that the passage of rodents through the digestive tract heavily damages DNA in their bones and teeth although the extent of DNA damage depends on the location of the remains in the stomach of the predator and the duration they are subject to the attack of the gastric juices. Thus, a minute portion of DNA can be rather well preserved. It is likely that it is this portion that is prone to long-term preservation since we could show DNA to be preserved in rodent remains from the El Harhoura2 cave in Morocco in levels dated to ca. 6,000 and 44,000 years. We also performed experiments of monitored taphonomy and analyzed DNA degradation and the transformation of the microbiome in bones of mice buried for different time intervals covering a period of 2 years. These experiments shed light on the processes through which biological specimens turn into environmental specimens

Genomic distribution and transcription of solitary HERV-K LTRs.

The human genome contains a family of endogenous retroviruses, HERV-K, with sequence homology to the B-type mouse mammary tumor virus. We have now identified a single HERV-K LTR within the C-type-related human retroviral element S71. The HERV-K LTR is located in the antisense direction between the S71 gag and the pol gene, replacing the 5' half of S71 pol. A number of HERV- K LTR-related cDNA clones were detected by screening various human cDNA libraries with an S71 HERV-K LTR probe, indicating abundant transcription of HERV-K-related LTRs in human tissues. Sequence analysis of four cDNA clones revealed LTR sequences with a nucleotide identity of 70 to 90% with HERV-K10 LTR. Some HERV-K-related LTR sequences contain potential short open reading frames. The analyzed cDNA clones do not harbor any retroviral sequences other than those related to HERV-K LTRs. However, most of the solitary LTRs were found to be coexpressed with cellular sequences. Transcription of these LTRs is probably directed by external cellular promoters. We show that HERV-K LTR- like sequences entered the primate genome about 33-40 million years ago. We estimate the human genome to contain about 25,000 copies of HERV-K-related LTRs, which are distributed over most human chromosomes in an irregular manner

Past climate changes, population dynamics and the origin of Bison in Europe

International audienceBackground: Climatic and environmental fluctuations as well as anthropogenic pressure have led to theextinction of much of Europe’s megafauna. The European bison or wisent (Bison bonasus), one of the last wildEuropean large mammals, narrowly escaped extinction at the onset of the 20th century owing to hunting andhabitat fragmentation. Little is known, however, about its origin, evolutionary history and population dynamicsduring the Pleistocene.Results: Through ancient DNA analysis we show that the emblematic European bison has experienced severalwaves of population expansion, contraction, and extinction during the last 50,000 years in Europe, culminatingin a major reduction of genetic diversity during the Holocene. Fifty-seven complete and partial ancient mitogenomesfrom throughout Europe, the Caucasus, and Siberia reveal that three populations of wisent (Bison bonasus) andsteppe bison (B. priscus) alternately occupied Western Europe, correlating with climate-induced environmentalchanges. The Late Pleistocene European steppe bison originated from northern Eurasia, whereas the modernwisent population emerged from a refuge in the southern Caucasus after the last glacial maximum. A populationoverlap during a transition period is reflected in ca. 36,000-year-old paintings in the French Chauvet cave. Bayesiananalyses of these complete ancient mitogenomes yielded new dates of the various branching events during theevolution of Bison and its radiation with Bos, which lead us to propose that the genetic affiliation betweenthe wisent and cattle mitogenomes result from incomplete lineage sorting rather than post-speciation gene flow.Conclusion: The paleogenetic analysis of bison remains from the last 50,000 years reveals the influence ofclimate changes on the dynamics of the various bison populations in Europe, only one of which survived intothe Holocene, where it experienced severe reductions in its genetic diversity. The time depth and geographicalscope of this study enables us to propose temperate Western Europe as a suitable biotope for the wisentcompatible with its reintroduction