Interference of the dominant negative helix–loop–helix protein ID1 with the proteasomal subunit S5A causes centrosomal abnormalities

Abstract

The inhibitor of DNA-binding (ID) proteins are dominantnegative inhibitors of basic helix-loop-helix transcription factors that have multiple functions during development and cellular differentiation. High-level expression of some ID family members has been observed in human malignancies, and in some cases was correlated with poor clinical prognosis. Ectopic ID1 expression extends the life span of primary human epithelial cells, inhibits cellular differentiation and induces centrosome duplication errors, thus suggesting that ID1 may have oncogenic activities. ID1 can bind to the proteasomal subunit S5A/Rpn10, but the biological consequences of the interaction have not been studied in detail. Here, we show that ID1's ability to induce supernumerary centrosomes correlates with S5A binding. Similar to ID1, a fraction of the S5A protein localizes to centrosomal structures. Furthermore, partial depletion of S5A by RNA interference causes accumulation of cells with supernumerary centrosomes. These results are consistent with the model that ID1 dysregulates centrosome homeostasis at least in part by interfering with S5A activities at the centrosome.

Id1 Overexpression Induces Tetraploidization and Multiple Abnormal Mitotic Phenotypes by Modulating Aurora A

“…Some of which may be involved in the abnormal mitotic phenotypes induced by Id1. In line with other studies (Hasskarl et al, 2004(Hasskarl et al, , 2007, we also detected rapid induction of supernumerary centrosomes and centrioles at a significant rate in our immortalized epithelial cells transduced with Id1. Several proteins are involved in the regulation of centrosome duplication and tetraploidization.…”

“…The S5A subunit contains an ubiquitin-interacting motif domain involved in the recognition and shuttling of the polyubiquitinated substrates to the proteolytic 20S degradation chamber of the proteasome (Hershko and Ciechanover, 1998). The Id1⌬N and HLH domains are essential for binding to the S5A (Hasskarl et al, 2007), which interfere with the ubiquitin proteasome system. Id1 mutant that lacks the Cterminal domain (Id1⌬C) could still efficiently bind to the S5A proteasomal subunit (Hasskarl et al, 2007), and it may block the presentation and ubiquitination of Aurora A for proteasomal degradation, resulting in its incomplete destabilization.…”

“…A plausible explanation is that Id proteins could inactivate the ubiquitin proteasome system and affect the degradation of Aurora A in our study. Id1 could bind to various components of the 26S proteasome including the S5A subunit of the 19S proteasome (Anand et al, 1997;Hasskarl et al, 2007) and the JAB1 protein (Berse et al, 2004). The S5A subunit contains an ubiquitin-interacting motif domain involved in the recognition and shuttling of the polyubiquitinated substrates to the proteolytic 20S degradation chamber of the proteasome (Hershko and Ciechanover, 1998).…”

“…The Id1⌬N and HLH domains are essential for binding to the S5A (Hasskarl et al, 2007), which interfere with the ubiquitin proteasome system. Id1 mutant that lacks the Cterminal domain (Id1⌬C) could still efficiently bind to the S5A proteasomal subunit (Hasskarl et al, 2007), and it may block the presentation and ubiquitination of Aurora A for proteasomal degradation, resulting in its incomplete destabilization. Hence, the results in Figure 5E reflect the combination effects of Cdh1 binding to the Id1 C-terminus D box and S5A binding to the Id1 N terminus and the HLH domain.…”

“…Id1 could be localized to the centrosomes (Hasskarl et al, 2004), and ectopic overexpression of Id1 could rapidly induce supernumerary centrosomes in human foreskin keratinocytes, suggesting that Id1 could potentially contribute to carcinogenesis by centrosome amplification. Recently, the same group has reported that the ability of Id1 to induce supernumerary centrosomes may correlate with the interaction of Id1 with the proteosomal subunit S5A/Rpn10 (Anand et al, 1997;Hasskarl et al, 2007). In addition, Id2 contains a destruction-box (D-box) recognition sequence for interacting with the anaphase-promoting complex (APC/C) (Lasorella et al, 2006).…”