Role of Promyelocytic Leukemia (Pml) Sumolation in Nuclear Body Formation, 11s Proteasome Recruitment, and as2O3-Induced Pml or Pml/Retinoic Acid Receptor α Degradation

Abstract

Promyelocytic leukemia (PML) is the organizer of nuclear matrix domains, PML nuclear bodies (NBs), with a proposed role in apoptosis control. In acute promyelocytic leukemia, PML/retinoic acid receptor (RAR) α expression disrupts NBs, but therapies such as retinoic acid or arsenic trioxide (As2O3) restore them. PML is conjugated by the ubiquitin-related peptide SUMO-1, a process enhanced by As2O3 and proposed to target PML to the nuclear matrix. We demonstrate that As2O3 triggers the proteasome-dependent degradation of PML and PML/RARα and that this process requires a specific sumolation site in PML, K160. PML sumolation is dispensable for its As2O3-induced matrix targeting and formation of primary nuclear aggregates, but is required for the formation of secondary shell-like NBs. Interestingly, only these mature NBs harbor 11S proteasome components, which are further recruited upon As2O3 exposure. Proteasome recruitment by sumolated PML only likely accounts for the failure of PML-K160R to be degraded. Therefore, studying the basis of As2O3-induced PML/RARα degradation we show that PML sumolation directly or indirectly promotes its catabolism, suggesting that mature NBs could be sites of intranuclear proteolysis and opening new insights into NB alterations found in viral infections or transformation.

AXIN is an essential co-activator for the promyelocytic leukemia protein in p53 activation

“…The mutants also dampened the ability of AXIN to prevent cell growth as revealed by colony formation assays. Third, AXIN localization in PML-NBs depends on a functional PML, as PML 3SM fails to colocalize AXIN in the nuclear bodies (Supplementary Figure 9), in accordance with the previous finding that PML 3SM is able to form primary PML-NB but cannot recruit many other NB components including Daxx and SP100 (Lallemand-Breitenbach et al, 2001). Fourth, AXIN strongly promotes PML sumoylation that is a vital step for formation of PML-NBs.…”

SUMO modification of E1B-55K oncoprotein regulates isoform-specific binding to the tumour suppressor protein PML

“…The PML protein has first been described as the causal agent in acute promyelocytic leukaemia as a fusion with the RARa receptor generated by the chromosomal translocation t(15;17) (Ascoli and Maul, 1991;de The et al, 1991;Kakizuka et al, 1991;Chang et al, 1992;Goddard et al, 1992;Kastner et al, 1992;Pandolfi et al, 1992;Dyck et al, 1994;Koken et al, 1994;Weis et al, 1994;Melnick and Licht, 1999;. Since these initial findings, it has become evident that PML is a general tumour suppressor frequently deregulated in various tumour types (Gurrieri et al, 2004) most presumably involving secondary effects of PML bodies as sites of protein degradation (Lallemand-Breitenbach et al, 2001), transcriptional regulation (Li et al, 2000;Zhong et al, 2000), cellular senescence (Ferbeyre et al, 2000;Pearson et al, 2000;Bischof et al, 2002;Langley et al, 2002), tumour suppression (Salomoni and Pandolfi, 2002;Salomoni et al, 2008), DNA repair (Bischof et al, 2001;Carbone et al, 2002), apoptosis (Hofmann and Will, 2003;Takahashi et al, 2004) and epigenetic regulation (Torok et al, 2009). Interestingly, functional inactivation of the E1B-55K leucine-rich nuclear export sequence (NES) induces enhanced posttranslational modification of E1B-55K by the small ubiquitin-related modifier 1 (SUMO1) at lysine 104 (SUMO-conjugation motif, SCM) as well as augments transformation of primary rat cells involving the accumulation of p53, E1B-55K and PML in subnuclear aggregates (Endter et al, 2001(Endter et al, , 2005.…”

Body language: the function of PML nuclear bodies in apoptosis regulation

“…[3][4][5][6][7] Besides a number of viral proteins, to date more than 40 different cellular proteins have been found in association with PML-NBs ( Figure 1). Although the molecular function of PMLNBs is currently not clear, there is accumulating evidence that PML-NBs are regulatory domains involved in various biological processes, including protein degradation, 5 transcriptional regulation, 8,9 cell growth, 10,11 antiviral response, 12,13 cellular senescence, [14][15][16][17] tumour suppression, 18 DNA repair 19,20 and apoptosis. [21][22][23][24][25] However, how can one explain that so many different and unrelated processes are linked to these nuclear domains?…”