Wasted (wst) mice have 3-bp deletion in the PCNA promoter

摘要

Mice homozygous for the autosomal recessive wasted mutation (wst/wst) have abnormalities in T-lymphocytes and in the anterior motor neuron cells of the spinal cord, leading to sensitivity to ionizing radiation, hind limb paralysis, and immunodeficiency. This defect results in a failure to gain weight by 20 days and death at 28 days of age. Previous results from the authors' group have shown that (1) wasted mice have little if any detectable PCNA protein or mRNA in thymus, but levels in liver, brain, and other tissues are similar to those in controls; and (2) the coding region for PCNA is the same in wasted mice and in control littermates. These observations gave rise to the present study, in which the PCNA promoter was sequenced for wst/wst mice, control littermates ((center dot)wst/+) and BCF(sub 1) (or BALB/c x C57BL/6) F(sub 1) controls. Sequence analysis revealed only one difference between wst/wst and BALB/c x C57BL/6 F(sub 1) littermates: a 3-bp deletion in the 5 foot upstream region of the PCNA gene of wasted mice that was observed on only one allele or no alleles of normal littermates. The mutated sites in PCNA promoter from two litters plus two additional wst/wst and two known wst/+ animals were screened with 8G and 11G probes, and each confirmed this pattern. The short term DNA segment encompassing the deletion was shown in gel shift experiments to bind a nuclear protein(s) present in a broad variety of cells including thymus and spleen nuclear extract from wst/wst and control mice. The mutated oligomer that was homozygous only in wst/wst mice was not able to bind the same nuclear protein(s).