DNA ligase IV functions in DNA nonhomologous end-joining and V(D)J recombination. Four patients with features including immunodeficiency and developmental and growth delay were found to have mutations in the gene encoding DNA ligase IV (LIG4). Their clinical phenotype closely resembles the DNA damage response disorder, Nijmegen breakage syndrome (NBS). Some of the mutations identified in the patients directly disrupt the ligase domain while others impair the interaction between DNA ligase IV and Xrcc-4. Cell lines from the patients show pronounced radiosensitivity. Unlike NBS cell lines, they show normal cell cycle checkpoint responses but impaired DNA double-strand break rejoining. An unexpected V(D)J recombination phenotype is observed involving a small decrease in rejoining frequency coupled with elevated imprecision at signal junctions.
Summary
In this study the saturated and aromatic hydrocarbon fractions of a marl sample from a Messinian (late Micoene) evaporitic basin located in the northern Apennines, and four oils, Rozel Point oil (Utah, USA; Miocene) and three seep oils from Sicily (Messinian), have been studied by GC with simultaneous FID and FPD detection and by GC-MS. All samples show characteristics which might be linked to hypersaline conditions prevailing during the time of deposition. Some of these characteristics are: a very low pristane/phytane ratio (<0.1), a relatively high abundance of docosane (C
22
) and gammacerane and a series of extended hopanes and/or hop-17(21)-enes maximizing at C
35
. The aromatic hydrocarbon fraction of all samples is dominated by organic sulphur compounds of which 2,3-dimethyl-5-(2,6,10-trimethylundecyl) thiophene is the most abundant compound. The suggestion of Meissner
et al.
(1984), that the source rock of Rozel Point oil was deposited under hypersaline conditions in a playa-like system, is supported by the organic geochemical characteristics of this oil.
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