Neither HMG-14a nor HMG-17 gene function is required for growth of chicken DT40 cells or maintenance of DNaseI-hypersensitive sites

Abstract

HMG-14 and HMG-17 form a family of ubiquitous non-histone chromosomal proteins and have been reported to bind preferentially to regions of active chromatin structure. Our previous studies demonstrated that the chicken HMG-17 gene is dispensable for normal growth of the DT40 chicken lymphoid cell line. Here it is shown that the major chicken HMG-14 gene,HMG-14a, is also dispensable and, moreover, that DT40-derived cells lacking both HMG-17 and HMG-14a proteins show no obvious change in phenotype with respect to the parental DT40 cells. Furthermore, no compensatory changes in HMG-14b or histone protein levels were observed in cells lacking both HMG-14a and HMG-17, nor were any alterations detected in such hallmarks of chromatin structure as DNaseI-hypersensitive sites or micrococcal nuclease digestion patterns. It is concluded that the HMG-14a and HMG-17 proteins are not required for normal growth of avian cell linesin vitro, nor for the maintenance of DNaseI-hypersensitive sites in chromatin.

The nucleosome‐binding protein HMGN2 modulates global genome repair

“…In this study, we focused on HMGN2 and used cells that lack HMGN2 and null cells for both HMGN1a and HMGN2 (as HMGN1a is partially homologous to HMGN2, and therefore it could, in theory, complement it). As previously described [25,26], the null DT40 cells lack either HMGN1a or HMGN2 or both HMGN1a and HMGN2, but they still contain HMGN1b, a relatively minor component in most chicken cells. The protein profiles of these cells differed slightly; however, all lines had normal proliferation and differentiation rates [25,26].…”

“…To investigate the involvement of HMGN variants in the UV response of DT40 cells, we used cells lacking either HMGN2 (clone D108‐1), or HMGN1a (clone 8/bsr8), or cells lacking both HMGN2 and HMGN1a (clones Nh43, Bp39, Nh52, and Bp5). The Bp lines were derived by first deleting the HMGN2 gene, and the Nh lines were derived by first targeting the HMGN1a gene [25,26]. We used western analysis to verify that the targeted genes were indeed disrupted (Fig.…”

“…It is important to note that the differences between the null cell lines D108‐1 and Nh43 and the wild‐type DT40 cells cannot be attributed to random mutations that may have accumulated in these cells, but only to the lack of HMGN proteins. The reason for excluding this possibility is that the two null cell lines were independently derived from DT40 cells; Nh43 cells were first disrupted for HMGN1a alleles and then for the two HMGN2 alleles, so they were not derived from the D108‐1 ( HMGN2 −/− ) cells [25,26].…”

Biological Functions of HMGN Chromosomal Proteins

“…Thus, in mice, loss of HMGN impairs repair of DNA damaged by either UV or ionizing radiation. Likewise, although DT40 chicken cells lacking either HMGN1, HMGN2 or both these variants survive [63], they are hypersensitive to UV irradiation. In these cells, loss of HMGNs increased the extent of G2-M checkpoint arrest and apoptosis [64].…”

HMGN1 is dispensable for myogenesis and adipogenesis

“…Interruption of HMGN1, HMGN2 or both in chicken DT40 cells caused no growth abnormalities, suggesting that these proteins are dispensable for cell growth in this background (Li et al, 1997;Li and Dodgson, 1995). However, other studies demonstrated that HMGN1 could prevent myogenesis when ectopically expressed in myoblasts, implying a role for HMGN1 in cellular differentiation (Pash et al, 1993).…”